Diagnosis Of Hypophosphatasia Research Articles

Possible role of bone turnover markers in the diagnosis of adult hypophosphatasia.

Hypophosphatasia (HPP) is a rare disorder of the bone metabolism, characterized by genetically-determined low alkaline phosphatase (ALP) activity. Low ALP may also be observed in some common causes of bone fragility, such as in osteoporosis treated with antiresorptive drugs. This study aimed to verify whether differences in bone turnover markers (BTMs) could help differentiate adult patients with HPP from those with osteoporosis undergoing antiresorptive treatment. In this multicenter study, we enrolled 23 adult patients with a diagnosis of HPP and compared them with 46 osteoporotic subjects previously treated with zoledronic acid or denosumab. BTMs such as C-terminal telopeptide of type I collagen (CTX), N-terminal propeptide of type I procollagen (P1NP), total ALP, and bone ALP (bALP) were measured, and ratios between BTMs were also calculated. Considering that the control group included only females, in the primary analysis we compared their characteristics with that of the 16 female patients with HPP. Both individual BTMs (CTX and P1NP) and four BTM ratios (ALP/P1NP, bALP/P1NP, ALP/CTX, and bALP/CTX) showed satisfactory discriminatory power, outperforming ALP alone. P1NP, in particular, had an AUC of 0.962 with a cut-off of 32μg/L, while as for the BTMs ratios, the ALP/P1NP ratio had an AUC of 0.964 with a cut-off of 1.114. Similar results were confirmed when including male HPP patients, when adjusting for age and sex, and finally when performing a sensitivity analysis only in patients with ALP less than or equal to 32U/L (i.e., the median of the distribution of the entire population). In cases of low ALP and bone fragility, BTM and their ratios could help distinguish HPP patients from osteoporotic individuals treated with antiresorptive drugs, aiding in accurate diagnosis and reducing the risk of inappropriate treatment.

7655 Genetic Mysteries Unveiled: Unusual Mutation Unraveled In Hypophosphatasia

Abstract Disclosure: A. Sharma: None. P. Katikaneni: None. S. Tanveer: None. K. Selk: None. Introduction: Hypophosphatasia (HPP), an inherited dental-osseous metabolic illness, is caused by inactivating mutations in the gene encoding the tissue-nonspecific isoenzyme of alkaline phosphatase (TNSALP), which leads to a decrease in TNSALP enzymatic activity. Patients with HPP typically experience dental and skeletal mineralization issues as their most common symptoms; musculoskeletal abnormalities, numerous fractures, tiredness, and migraines are less common clinical presentations. Case Report: Our 75-year-old male patient initially presented 1.5 years prior following a spontaneous T12 vertebral fracture. A bone biopsy was performed and did not reveal evidence of malignancy. Testing for SPEP/UPEP was not consistent with myeloma, and thyroid testing was also unrevealing. His alkaline phosphatase level was consistently <40 IU/L since 1999. An evaluation was done for low alkaline phosphatase and secondary reasons for bone loss. This testing did not reveal vitamin D deficiency, parathyroid disease, hypophosphatemia, laboratory evidence of celiac disease, hypogonadism, or hypomagnesemia. A vitamin b6 level was markedly elevated at 119 ng/mL (ref range 2.1-21.7) while not on supplementation. He had noticed multiple fractures as a child, but he had written them off as minor injuries. He could clearly remember breaking his right wrist and clavicle. As an adult, he had rib fractures and a foot fracture. He was unable to recollect losing his primary teeth. Almost all his teeth are crowns or implants despite taking exceptional care of them. He did not have joint hypermobility. Genetic testing revealed the patient was heterozygous for an ALPL gene variant, c.876_882delinsT. It was a variant of undetermined significance at that time. His daughter also was found to have a low alkaline phosphatase and the same genetic test result. She also has experienced dental carries and joint pain. Our patient initiated teriparatide due to the need for more urgent therapy for extensive spinal surgery. He was later transitioned to asfotase alfa therapy and has not had any further fractures at the time of this report. Discussion: Hypophosphatasia is a rare inborn disorder due to mutations in the tissue nonspecific alkaline phosphatase gene ALPL and is characterized by low ALP levels. Affected individuals will also have elevated vitamin b6 levels and urinary phosphoethanolamine (PEA) levels. Early diagnosis of HPP is necessary to prevent bone fracture pain and improve quality of life. Inaccurate assessments can miss diagnoses of parents and other family members and even lead to lost opportunities to treat a patient with a substantial illness burden. This case highlights the mutation c.876_882delinsT as a likely pathologic variant in the ALPL gene. It also supports that patients with HPP can also respond to teriparatide treatment. Presentation: 6/2/2024

Impact of Restricted Phosphorus, Calcium-adjusted Diet on Musculoskeletal and Mental Health in Hypophosphatasia.

Impairments in musculoskeletal and mental health are common in adults with Hypophosphatasia (HPP). Restricted phosphorus intake has been suggested to positively affect symptoms in HPP, but there is a lack of interventional evidence. This work aimed to evaluate the effect of a phosphorus-restricted, calcium-adjusted diet on musculoskeletal and mental health in HPP. A prospective, noncontrolled, single-center interventional study (NuSTEPS II) was conducted among outpatients at the Osteology Department, University of Wuerzburg, Germany. A total of 26 adults with an established HPP diagnosis received a standardized diet with a defined daily intake of phosphorus (1160-1240 mg/d) and calcium (870-930 mg/d) over 8 weeks. Main outcome measures were functional testing and patient-reported outcome measures. At 8 weeks, significant improvements were observed in usual gait speed (P = .028) and the chair-rise test (P = .019), while no significant changes were seen in the 6-minute walk test (P = .468) and the timed up-and-go test (P = .230). Pain was not significantly reduced according to the visual analog scale (VAS) (P = .061), pain subscale of the 36-Item Short-Form Health Survey (SF-36) (P = .346), and Pain Disability Index (P = .686). Further, there was a significant improvement in the SF-36 vitality subscale (P = .022) while all other subscales as well as the Lower Extremity Functional Scale (P = .670) and the Fatigue Assessment Scale (P = .392) did not change significantly. Adjustments of mineral intake were not associated with relevant alterations regarding the intake of energy and energy-supplying nutrients or body composition. Adjusting phosphorus and calcium intake may positively affect individual symptoms in adults with HPP, but overall clinical effectiveness regarding major issues like pain and endurance appears limited.

The challenge of hypophosphatasia diagnosis in adults: results from the HPP International Working Group Literature Surveillance.

Hypophosphatasia (HPP) is an inborn error of metabolism caused by reduced or absent activity of the tissue non-specific alkaline phosphatase (TNSALP) enzyme, resulting from pathogenic variants in the ALPL gene. Clinical presentation of HPP is highly variable, including lethal and severe forms in neonates and infants, a benign perinatal form, mild forms manifesting in adulthood, and odonto-HPP. Diagnosis of HPP remains a challenge in adults, as signs and symptoms may be mild and non-specific. Disease presentation varies widely; there are no universal signs or symptoms, and the disease often remains underdiagnosed or misdiagnosed, particularly by clinicians who are not familiar with this rare disorder. The absence of diagnosis or a delayed diagnosis may prevent optimal management for patients with this condition. Formal guidelines for the diagnosis of adults with HPP do not exist, complicating efforts for consistent diagnosis. To address this issue, the HPP International Working Group selected 119 papers that explicitly address the diagnosis of HPP in adults through a Medline, Medline In-Process, and Embase search for the terms "hypophosphatasia" and "HPP," and evaluated the pooled prevalence of 17 diagnostic characteristics, initially selected by a group of HPP clinical experts, in eligible studies and in patients included in these studies. Six diagnostic findings showed a pooled prevalence value over 50% and were considered for inclusion as major diagnostic criteria. Based on these results and according to discussion and consideration among members of the Working Group, we finally defined four major diagnostic criteria and five minor diagnostic criteria for HPP in adults. Authors suggested the integrated use of the identified major and minor diagnostic criteria, which either includes two major criteria, or one major criterion and two minor criteria, for the diagnosis of HPP in adults.

THU460 A Case Series Of Hypophosphatasia: Presentation And Response To Asfotase Alfa

Abstract Disclosure: F. Alsarraf: None. D.S. Ali: None. K. Almonaei: None. H. Al-Alwani: None. M. Brandi: Consulting Fee; Self; Aboca, Alexion Pharmaceuticals, Inc., Amolyt, Bruno Farmaceutici, Calcilytix, Kyowa Kirin, UCB. Grant Recipient; Self; Abiogen, Alexion Pharmaceuticals, Inc., Amgen Inc, Bruno Farmaceutici, Echolight, Eli Lilly & Company, Kyowa Kirin, SPA, Theramex, UCB. Speaker; Self; Abiogen, Alexion Pharmaceuticals, Inc., Amgen Inc, Bruno Farmaceutici, Calcilytix, Echolight, Eli Lilly & Company, Kyowa Kirin, SPA, Theramex, UCB. A.A. Khan: Advisory Board Member; Self; Amgen Inc, Amolyt, Takeda. Consulting Fee; Self; Amgen Inc. Grant Recipient; Self; Alexion Pharmaceuticals, Inc., Amgen Inc, Ascendis, Chugai, Radius Health, Inc, Takeda, Ultragenyx. Research Investigator; Self; Amgen Inc, Radius Health, Inc. Speaker; Self; Alexion Pharmaceuticals, Inc., Amgen Inc. Introduction: Hypophosphatasia (HPP) is a rare inherited metabolic bone disorder characterized by a deficiency in the tissue non-specific alkaline phosphatase (TNSALP) due to loss of function mutation in the ALPL gene. HPP is associated with impaired skeletal mineralization due to elevations in inorganic pyrophosphate and altered phosphate: pyrophosphate ratio. Asfotase alfa (AA) was approved for treatment of HPP in 2015. We present a case series of 7 patients with HPP, 5 with pediatric-onset and 2 with adult-onset, who have been treated with AA and describe the efficacy and safety in these patients. Case presentation: 7 patients (4 females, 3 males) aged 19-68 years with HPP were included in this case series. Diagnosis of HPP was confirmed by DNA analysis. AA was administered in doses of 6mg/kg/week with a mean follow-up of 6 months (SD= 5). Management outcome: Improvement in muscle strength, muscle pain, walking ability and walking distance with a reduction in the use of gait aids was seen. Muscle strength and pain improved by up to 70% from baseline as quantified subjectively by patients. Walking distance improved by up to 100%. Patients also reported improved cognition, mood and energy levels, with up to 90% improvement in mood and 75% improvement in energy levels. 4 out of 6 patients first noted clinical signs of improvement after 3 months of being on therapy. 1 out of the 7 patients sustained a toe fracture 10 months from being on AA. AA was well-tolerated with injection site reactions being the most commonly reported adverse effect. Discussion: HPP treatment with AA in individuals with both pediatric and adult-onset forms resulted in significant improvement in musculoskeletal and cognitive manifestations in addition to patients’ quality of life. It was well tolerated in 6 patients. 1 patient discontinued therapy because of minor adverse effects with myalgias. Presentation: Thursday, June 15, 2023

THU458 Demineralization Zebras: A Rare Case Of Hypophosphatasia In An Adult Presenting With Osteopenia

Abstract Disclosure: B.P. Ramchandani: None. A. Khan: None. H. Aftab: None. Introduction: Hypophosphatasia (HPP) is a rare genetic bone disease with only 500-600 cases reported in the United States. It is characterized by mutations in the tissue non-specific alkaline phosphatase (TNSALP) gene, leading to impaired bone mineralization. HPP presenting in the perinatal period is fatal. During infancy, rachitic deformities develop by age 6 months. Children present with early loss of deciduous teeth and delayed milestones while in adulthood, HPP is characterized by recurrent fractures, osteoporosis, and muscle weakness. We describe a case of HPP diagnosed in a patient after low ALP was discovered on laboratory testing. Case: A 69-year-old female presented for the evaluation of osteopenia. She had a history of fracture of the right knee as well as fracture of the base of the right 5th metatarsal and lateral aspect cuboid, which healed well with conservative management. Dental history was significant for 5 implants over the last 15 years. She was on vitamin D supplements and had also taken risedronate for osteopenia for 14 years which was discontinued at her first visit with us. Family history was significant for osteoporosis in her mother. Initial lab studies were significant for an ALP of 29 U/L (ref range 39-113 U/L), phosphate of 4.9 mg/d (ref range 2.4-4.8 mg/dl), pyridoxal 5’-phosphate level (vitamin B6) of 308 nmol/L (ref range 20-125 nmol/l), a vitamin D 25-OH level of 20 ng/mL (ref range >30 ng/ml) and PTH of 49 pg/dl (ref range 15-88 pg/ml). Repeat lab testing done 6 months after stopping risedronate showed consistent similar results with an ALP of 32 U/L, phosphate level of 5.1 mg/dl, vitamin B6 level of 349 nmol/L, and vitamin D 25OH level of 26 ng/mL. Bone density scan revealed a lumbar spine BMD of 1.503 g/cm2 (T-score 2.5) and a mean total hip BMD of -0.3 consistent with osteoporosis of spine and osteopenia of hip. Genetic testing and counseling were offered to the patient, however she declined. Discussion: Our patient presented with recurrent fractures and loss of dentition requiring multiple dental implants in the background of osteopenia. Given persistently low serum ALP and elevated serum vitamin B6 levels her presentation suggested a diagnosis of HPP. Management includes supportive treatment with prompt treatment of fractures, and routine dental care. Although there is no approved medication for adults, enzyme therapy replacement with asfotase-alfa (a recombinant human ALP) is FDA-approved for pediatric-onset HPP which improves bone mineralization and muscle strength, however discontinuation of therapy leads to reappearance of bone hypomineralization. Once the diagnosis is made, genetic testing and counseling should be offered to prevent complications in future pregnancies. Presentation: Thursday, June 15, 2023

THU410 Retrospective Review Of Adults Patients With Suspected Or Confirmed Hypophosphatasia At The Penn Bone Center

Abstract Disclosure: R. Tran: None. C. Hvisdas: None. M. Riordan: None. L. Novotny: None. S. Kallish: None. K. Patel: None. M. Al Mukaddam: None. Abstract: Hypophosphatasia (HPP) is a rare inherited genetic disorder that affects the mineralization of bones and teeth. HPP is the result of a pathogenic variant involving the tissue nonspecific alkaline phosphatase (ALPL) gene. The clinical presentations of HPP greatly vary from serious perinatal manifestations (respiratory failure, seizures, and death) to mild manifestations in adulthood. In adults, hallmark signs and symptoms include early loss of primary or secondary teeth, osteoporosis, osteomalacia, recurring metatarsal stress fractures, and abnormal laboratory values, such as low alkaline phosphatase (ALP), elevated phosphoethanolamine, and elevated vitamin B6.The treatment and follow up of adults with HPP are not clearly described. This retrospective study characterizes 43 patients referred to the Penn Bone Center for suspected HPP. Twelve of the 43 patients had a confirmed HPP diagnosis based on both clinical presentations and evidence of variant in the ALPL gene. The twelve patients consisted of both female and male adults between the ages of 24 to 74. In addition, the patients had abnormal ALP levels, ranging between less than 5 to 38 units per liter (normal range: 38 to 126 U/L). Six of these patients had previous or current use of asfotase alfa with variable treatment response. Two patients decided to stop treatment due to lack of clinical benefit or worsening of symptoms while on asfotase alfa therapy. Biochemical and bone mineral density follow-up while on therapy has not been shown to be helpful in monitoring treatment response. Asfotase alfa is a subcutaneously administered synthetic human alkaline phosphatase that was approved by the Federal Drug Administration (FDA) in 2015 for treatment of perinatal/infantile- and juvenile-onset hypophosphatasia. However, the efficacy of treatment in adults remain unclear at this time. Further research is required to better define the natural progression of mild or adult-onset hypophosphatasia and the patients who would benefit from enzyme therapy. Presentation: Thursday, June 15, 2023

Not just a carrier: Clinical presentation and management of patients with heterozygous disease-causing alkaline phosphatase (ALPL) variants identified through expanded carrier screening.

Hypophosphatasia (HPP) is an underrecognized, complex bone mineralization disorder with variable manifestations caused by one or two deleterious variants in the alkaline phosphatase (ALPL) gene. Expanded carrier screening (ECS), inclusive of ALPL, intends to inform reproductive risk but may incidentally reveal an HPP diagnosis with 50% familial risks. We sought to investigate at-risk individuals and develop a multidisciplinary referral and evaluation protocol for ECS-identified ALPL heterozygosity. A retrospective database query of ECS results from 8 years to 1 month for heterozygous pathogenic/likely pathogenic ALPLvariants was completed. We implemented a clinical protocol for diagnostic testing and imaging, counseling, and interdisciplinary care management for identified patients, and outcomes were documented. Heterozygous ALPL variants were identified in 12/2248 unrelated patients undergoing ECS (0.53%; heterozygote frequency 1/187). Of 10 individuals successfully contacted, all demonstrated symptomatology and/or alkaline phosphatase values consistent with HPP. ECS may reveal incidental health risks, including recognition of missed HPP diagnoses in ALPL heterozygotes. In our cohort, all ECS-identified ALPL heterozygotes with clinical and/or biochemical data available demonstrated features of HPP. Referral to a genetics professional familiar with HPP is indicated for family history assessment, genetic counseling, cascade testing, and long-term bone health management.

Urine phosphoethanolamine is a specific biomarker for hypophosphatasia in adults.

We investigated the utility of urine phosphoethanolamine (PEA) as a marker to aid in diagnosing and/or confirming hypophosphatasia (HPP) in adults and for monitoring patients on enzyme replacement therapy (ERT). Data was collected from seventy-eight adults who were referred to the Vanderbilt Program for Metabolic Bone Disease for evaluation of a possible or confirmatory HPP diagnosis between July 2014 through December 2019. Fifty-nine patients were diagnosed with HPP and nineteen were excluded from a diagnosis of HPP. The urine PEA results of those patients with a confirmed diagnosis of HPP and those patients with a diagnosis of HPP excluded were captured and compared to other laboratory and clinical parameters consistent with HPP, including alkaline phosphatase (ALP) activity, plasma pyridoxal 5'-phosphate (PLP), the presence of musculoskeletal abnormalities, and genetic testing for pathogenic mutations in ALPL. Initial urine PEA values in patients in our HPP cohort and not on ERT were significantly higher (median=150.0nmol/mg creatinine, IQR=82.0-202.0) compared patients in our HPP negative group (median 18.0nmol/mg creatinine, IQR=14.0-30.0, p<0.0001) and higher than patients on ERT (median 65.0nmol/mg creatinine, IQR=45.3-79.8). Patients who began ERT had a decline in urine PEA levels after treatment with a mean decrease of 68.1%. Plasma ALP levels were significantly lower in the group of patients with HPP and not on ERT group (median=24.0U/L, IQR=15.0-29.50) compared to the patients without HPP (median=45.50U/L, IQR=34.0-62.0;) and plasma PLP levels were significantly higher in the HPP non-ERT group (median=284.0nmol/L, IQR=141.0-469.4) compared to the patients without HPP (median=97.5nmol/L, IQR=43.7-206.0;). The area under the curve (AUC) of urine PEA, ALP, and PLP to distinguish between HPP and non-HPP patients is 0.968, 0.927 and 0.781, respectively, in our cohort. Urine PEA had 100% specificity (95% CI of 83.2% to 100.0%) for diagnosing HPP at a value >53.50nmol/mg creatinine with a sensitivity of 88.4%; 95%CI 75.5 to 94.9%. ALP had a 100% specificity (95% CI of 82.4% to 100.0%) for diagnosing HPP at a value <30.5U/L with a sensitivity of 77.2%; (95%CI 64.8 to 86.2%). PLP had a 100% specificity (95% CI of 81.6% to 100.0%) for diagnosing HPP at a value >436nmol/L with a sensitivity of 26.9%; (95%CI 16.8 to 40.3%). The most common pathogenic or likely pathogenic mutations in our cohort were c.1250A>G (p.Asn417Ser), c.1133A>T (p.Asp378Val), c.881A>C (p.Asp294Ala), c.1171C>T (p.Arg391Cys), and c.571G>A, (p.Glu191Lys). Urine PEA is a promising diagnostic and confirmatory marker for HPP in patients undergoing investigation for HPP. Urine PEA also has potential use as a marker to monitor ERT compliance. Future studies are necessary to evaluate the association between PEA levels and clinical outcomes.

Proposing a clinical algorithm for better diagnosis of hypophosphatasia in resource-limiting situations.

Early diagnosis of hypophosphatasia (HPP) is challenging. Here, we propose to broaden the diagnostic criteria of HPP by reviewing published data on BMD and fractures in HPP patients. Non-osteoporotic fractures and higher than normal lumbar BMD were recurrent in HPP patients and could be included as diagnostic criteria. HPP is a genetic disorder caused by autosomal recessive or dominant loss-of-function mutations in the ALPL gene that encodes for tissue-nonspecific alkaline phosphatase (TNSALP). Expressive genetic heterogeneity and varying severity of TNSALP deficiency lead to a wide-ranging presentation of skeletal diseases at different ages that coupled with HPP's rarity and limitation of biochemical and mutational studies present serious hurdles to early diagnosis and management of HPP. To widen the scope of HPP diagnosis, we assessed the possibility of areal bone mineral density (BMD) as an additional clinical feature of this disease. PubMed, Web of Science, and ScienceDirect were searched with the following keywords: ("Hypophosphatasia OR HPP") AND ("Bone Mineral Density OR BMD") AND "Human". Studies and case reports of subjects with age ≥ 18years and having BMD data were included. We pooled data from 25 publications comprising 356 subjects (90 males, 266 females). Only four studies had a control group. Biochemical hallmarks, pyridoxal 5'-phosphate (PLP) and phosphoethanolamine (PEA), were reported in fifteen and six studies, respectively. Twenty studies reported genetic data, nineteen studies reported non-vertebral fractures, all studies reported lumbar spine (LS) BMD, and nineteen reported non-vertebral BMD. Higher than normal and normal BMD at LS were reported in three and two studies, respectively. There was marked heterogeneity in BMD at the non-vertebral sites. Higher than normal or normal LS BMD in an adult with minimal or insufficient fractures, pseudofractures, non-healing fractures, fragility fractures, and stress fractures may be included in the diagnostic protocol of HPP. However, genetic testing is recommended for a definitive diagnosis.

The Clinical Picture of Patients Suffering from Hypophosphatasia-A Rare Metabolic Disease of Many Faces.

Hypophosphatasia (HPP) is a rare, and usually diagnosed with delay, genetic disease caused by a mutation in the alkaline phosphatase liver/bone/kidney type (ALPL) gene. Low activity of the alkaline phosphatase (ALP) impairs the hydroxyapatite formation, reducing skeletal mineralization. The aim of the study was to present patients diagnosed with HPP. The data from the history and medical records of patients were analyzed. In the study group, one patient was diagnosed with perinatal type of HPP, three were diagnosed with infant variant, eight were diagnosed with children variant, two were diagnosed with odontohypophosphatasia, and two were diagnosed with the adult type of the disease. The most frequently presented symptoms included premature loss of teeth in 11/16 (68.75%) patients, bone deformities in 10/16 (62.5%) patients, chronic bone pain in 9/16 (56.25%) patients, and fractures in 8/16 (50%) patients. Reduction in bone mineral density in at least one examined projection has been found in 11/14 patients. Conclusions: The correct diagnosis of HPP is difficult due to the variety of types and clinical symptoms, as well as the very rare occurrence of this disease. Both lower and upper reference values of the determined biochemical parameters may be important in HPP diagnostics.

Cross-sectional analysis: clinical presentation of children with persistently low ALP levels.

Low activity of serum alkaline phosphatase (ALP) is a hallmark of hypophosphatasia (HPP), but low readings of ALP are not always recognized in clinical routine. Understanding the clinical presentations associated with low ALP may contribute to a timelier diagnosis of HPP. Data from paediatric patients with low ALP, excluding patients in intensive care and with oncological/haematological disorders, were analysed. Most recent ALP values, previous diagnoses, medication and relevant symptoms were extracted from patient records at nine specialised centres and analysed descriptively. A relationship between body height and ALP values was scrutinised by linear regression. Of 370 children, 15 (4.1%) had a diagnosis of HPP. In the subgroup without a diagnosis of HPP, 241 (67.9%) out of 355 patients had one or more medical conditions known to be associated with low serum ALP. Of those, hypothyroidism, malnutrition and steroid administration were most frequent. Characteristic symptoms, particularly, short stature, muscle weakness and delay of motor development were more frequent and ALP values were lower in patients with documented HPP diagnosis compared to patients without diagnosis of HPP (Ø z-scores:-2.52) (interquartile range [IQR]=0.20) vs.-1.96 (IQR=0.87). A weak positive linear relationship between z-scores of ALP and body height was identified (p<0.001). This analysis of paediatric patient records elucidates a wide range of disorders associated with low ALP activity. In case of additional specific symptoms, HPP should always be considered as a differential diagnosis.

Diagnosis of Hypophosphatasia in Adults Presenting With Metatarsal Stress Fracture: Proof-of-Concept for a Case-Finding Strategy.

ABSTRACTHypophosphatasia (HPP) is caused by loss‐of‐function mutations in ALPL resulting in decreased alkaline phosphatase (ALP) activity. Metatarsal stress fracture (MSF) is a common clinical feature of hypophosphatasia in adults. In this study, the primary objectives were to determine whether new cases of ALPL variants could be identified in patients with MSF and who also had serum ALP concentration below the reference range and to phenotype their clinical course. Electronic health records were queried for adult patients with MSF using International Classification of Disease codes (ICD‐9, ICD‐10CM) and ALP measurements. Patients with ALP levels below the normal limit were invited to receive mutational analysis of ALPL and to complete the following surveys: the Short Form 36 version 2 (SF36v2), the Brief Pain Inventory‐Short Form (BPI), and the Health Assessment Questionnaire Disability Index (HAQ‐DI). Cases with and controls without ALPL pathogenic variants were compared by survey scores and clinical variables relevant to fracture. In 1611 patients with MSF presenting to a podiatry clinic (10/1/2011–10/1/2017), 937 had ALP measurement, of whom 13 (1.4%) had ALP levels below the lower normal limit. In eight patients consenting to participate, two had heterozygous pathogenic ALPL variants. ALPL variants were found in 2 of 1611 patients (0.12%) with MSF, 2 patients of 937 (0.21%) in those with MSF and any ALP measurement, and 2 of 13 patients (15%) in MSF and decreased ALP level. Cases versus controls rated lower scores on eight of eight SF36v2 scales (range, 0–100); higher scores for worst pain (8.0 vs. 0.8) and average pain (6.0 vs. 0.7) on the BPI (range, 0–10); and higher standard disability score (1.4 vs. 0) on the HAQ‐DI (range, 0–3). These data provide proof‐of‐concept for HPP case identification in patients presenting to a podiatry clinic with MSF, suggesting a search for historically low ALP levels may be a useful step for consideration of HPP diagnosis, and supports a prospective study to determine an optimal case‐finding strategy. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Predictive modeling of hypophosphatasia based on a case series of adult patients with persistent hypophosphatasemia.

Hypophosphatasemia is a condition in which low levels of alkaline phosphatase (ALP) are detected in the serum. Some individuals presenting with this condition may have a rare genetic disease called hypophosphatasia (HPP), which involves mineralization of the bone and teeth. Lack of awareness of HPP and its nonspecific symptoms make this genetic disease difficult to diagnose. We developed a predictive model based on biomarkers of HPP such as ALP and pyridoxal 5'-phosphate (PLP), because clinical manifestations sometimes are not recognized as symptoms of HPP. We assessed 325,000 ALP results between 2010 and 2015 to identify individuals suspected of having HPP. We performed univariate and multivariate analyses to characterize the relationship between hypophosphatasemia and HPP. Using several machine learning algorithms, we developed several models based on biomarkers and compared their performance to determine the best model. The final cohort included 45 patients who underwent a genetic test. Half (23 patients) showed a mutation of the ALPL gene that encodes the tissue-nonspecific ALP enzyme. ALP (odds ratio [OR] 0.61, 95% confidence interval [CI] 0.3-0.8, p = 0.01) and PLP (OR 1.06, 95% CI 1.01-1.15, p = 0.04) were the only variables significantly associated with the presence of HPP. Support vector machines and logistic regression were the machine learning algorithms that provided the best predictive models in terms of classification (area under the curve 0.936 and 0.844, respectively). Given the high probability of a misdiagnosis, its nonspecific symptoms, and a lack of awareness of serum ALP levels, it is difficult to make a clinical diagnosis of HPP. Predictive models based on biomarkers are necessary to achieve a proper diagnosis. Our proposed machine learning approaches achieved reasonable performance compared to traditional statistical methods used in biomedicine, increasing the likelihood of properly diagnosing such a rare disease as HPP.

Hypophosphatasia screening in pediatric age based on records

Introduction: hypophosphatasia (HPP) is a congenital disease, characterized by a defect in bone and dentary mineralization, secondary to a deficiency in the biosynthesis of non-specific tissue isoenzyme of alkaline phosphatase (TNSALP), resulting in decreased levels of alkaline phosphatase (ALP) activity and the extracellular accumulation of its substrates. Our goal was to establish the interest of screening the hospital databases of pediatric patients with low levels of ALP for the diagnosis of HPP. Materials and methods: during the period from September 2016 to September 2017, 23231 patients were tested for ALP, 1752 of them showed low levels of ALP. Based on the clinic, basal disease and that in previous analyses they did not present ALT norm values, 14 cases were selected: 8 cases associated with early puberty, 1 case of low size, 1 case of liver disease and myasthenia and 1 case of teething problems. ALPL gene was studied in those cases. Results: the latter case was of an 8-year-old male with a pathological variant of HPP: c.343_348dupACCGCC (p.Thr115_Ala116dup) in exon 5 in dominant heterozygous, inherited from his mother. At the substrate level the levels of pyridoxal-5-phosphate were above 50μg/L. Conclusion: the diagnostic strategy with a high index of clinical suspicion of HPP should include the observation of low levels of serum ALP activity. Our study shows that HPP is an underdiagnosed disease.An appropriate protocol to detect HPP in a clinical setting in tertiary care hospitals is required.

Нерешенные вопросы диагностики гипофосфатазии: мнение экспертов

Hypophosphatasia (HPP) is a rare hereditary metabolic disease resulting from the loss-of-function mutation in the ALPL gene encoding tissue-nonspecific alkaline phosphatase (ALP). Clinical presentations are polymorphic and manifest themselves differently depending on the age of disease onset and severity. The occurrence of mild disease, including adult HPP, is challenging to assess due to the high heterogeneity of clinical signs and a lower diagnosis rate. Doctors’ awareness of HPP is the fundamental factor affecting its detection rate. This paper reviews the conclusions of the Expert Council on HPP diagnosis and potentialities to improve diagnosis. Ten experts from various Russian regions participated in panel sessions. Each member shared the experience and established practice on the diagnosis of orphan diseases in his/her region and gave suggestions to optimize the diagnostic approach to HPP. The result was the development of a management algorithm and routing of patients from identifying symptoms to decision making on prescribing enzyme-replacement therapy and subsequent follow-up at every level of medical care . KEYWORDS: hypophosphatasia, alkaline phosphatase, orphan diseases, ALPL, enzyme-replacement therapy, routing. FOR CITATION: Zakharova E.Yu., Varlamova T.V., Voronin S.V. et al. Unsolved diagnostic issues of hypophosphatasia: Expert Council. Russian Medical Inquiry. 2021;5(9):605–614 (in Russ.). DOI: 10.32364/2587-6821-2021-5-9-605-614.

Clinical and biochemical characteristics of adults with hypophosphatasia attending a metabolic bone clinic.

This study sought to identify the clinical and biochemical characteristics that would help distinguish hypophosphatasia (HPP) from other metabolic bone diseases in adult patients attending a metabolic bone clinic by comparing patients who have genetically confirmed HPP with a group of patients with low bone mineral density (BMD) in the osteoporotic or osteopenic range. Data were collected from February 2016 to October 2018 for 41 patients (n=20 in the HPP group, n=21 in the low-BMD group) attending the metabolic bone clinic at Sheffield, United Kingdom (UK) or who were recruited via the Rare UK Diseases Study (RUDY) platform during the same period. A study questionnaire was administered to all patients, and assessments were conducted for laboratory values, physical functions, BMD, and spine imaging. Patients with HPP were characterized as being younger, more likely to have metatarsal or femoral shaft fractures, and less likely to have vertebral fractures compared with patients in the low-BMD group. The HPP group had lower total and bone-specific alkaline phosphatase, higher pyridoxal 5'-phosphate (PLP), and lower, albeit sufficient, 25-hydroxyvitamin D. Low-BMD group had lower C-terminal telopeptide and tartrate-resistant acid phosphatase 5b (61.9% were on bisphosphonates at enrollment). Dual X-ray absorptiometry (DXA) analysis found that the HPP group had higher total hip and lumbar BMD T- and Z-scores compared with the low-BMD group. There were no differences found between the two groups with physical functional assessments. Results of receiver operating characteristic analysis indicated strong diagnostic accuracy of these biomarkers for HPP. Thresholds of total alkaline phosphatase (ALP) activity of 43IU/L or less and PLP level of 120nmol/L or more were determined to be potentially clinically useful for distinguishing HPP from other metabolic bone diseases. This study supported the use of ALP and PLP measurements as predictive of HPP diagnosis along with certain demographic and clinical characteristics (younger age, metatarsal or femoral fractures without low mean BMD T- and Z-scores on a DXA scan) that can aid in recognizing adults who should be further evaluated for HPP. The critical values identified need to be applied to an independent sample to be tested for diagnostic accuracy.

Effects of Enzyme Replacement Therapy for Primary Teeth in a Patient with Infantile Hypophosphatasia

Hypophosphatasia (HPP) is a skeletal disorder characterized by hypomineralization of bone, with early exfoliation of primary teeth. Alkaline phosphatase enzyme replacement therapy (ERT) has been shown to improve bone hypomineralization for patients with HPP, although its dental effects are unknown. A 20-month-old Japanese boy diagnosed with infantile HPP was referred to our clinic because of early exfoliation of primary teeth. The patient had been followed by a pediatrician since the age of 3 months, due to slow weight gain. At the age of 12 months, primary incisors showed sudden exfoliation; at the age of 19 months, a diagnosis of HPP was made based on bone and dental manifestations. ERT was initiated at the age of 21 months. The patient demonstrated stable periodontal conditions of primary molars that erupted after initiation of ERT, due to improved alveolar bone and tooth mineralization. Thus, ERT may improve both dental and systemic conditions.

MON-341 New Diagnosis of Hypophosphatasia in a 79-Year-Old Woman with Low Bone Density

Introduction: Hypophosphatasia is a rare metabolic bone disease caused by one of several mutations in the ALPL gene which encodes tissue nonspecific alkaline phosphatase (ALP). It is usually diagnosed in childhood and can have a heterogenous clinical presentation depending on the extent of enzyme deficiency. Here we report the oldest known patient with hypophosphatasia. Clinical Case: A 79-year-old woman with a history of medullary thyroid cancer (MTC) in remission, was referred to our metabolic bone disease clinic for the evaluation and treatment of osteopenia. She had suffered from numerous musculoskeletal complaints for several years and had received a diagnosis of polymyalgia rheumatica. However, her symptoms persisted despite a six month trial of prednisone. Although she had developed dental caries at a young age, she denied premature tooth loss. Her family history was significant for arthralgias and vertebral disc disorders in multiple family members, including both her children. Her mother carried a diagnosis of rheumatoid arthritis and osteoporosis. The only pertinent physical exam finding was short stature (Height -4’6”). A DEXA scan was performed using a Hologic unit and revealed a T Score of -1.0 at the L-spine and -1.9 at the femoral neck. A FRAX score predicted a 14% risk of major osteoporotic fracture and 4% risk of hip fracture.Laboratory data revealed: Serum Calcium 9.3 (8.5-10.5 mg/dL), Albumin 4.3 (3.5-5.0 g/dL), ALP 21 (<130 U/L), Vitamin D 25OH 46.2 (>30 ng/ml), Intact PTH 28.3 (15.0-65.0 pg/ml), Vitamin B6 87.7 (2-21 ng/ml).On review of her medical record, low ALP levels ranging between 20-30 U/L were noted to be present for the last twenty years. Given her history of musculoskeletal complaints, short stature, elevated Vitamin B6 and low ALP, genetic testing for hypophosphatasia was performed. Her results confirmed a known pathogenic mutation in the ALPL gene. Conclusion: This case highlights the importance of reviewing ALP levels and relevant patient history to rule out hypophosphatasia prior to initiating therapy for osteoporosis. This condition is often unrecognized. Bisphosphonates, which are often the first line of treatment in osteoporosis, are contraindicated in hypophosphatasia as they can increase the risk of atypical fractures.1 Teriparatide may improve bone density depending on the extent of ALP deficiency. Asfotase alfa is a new agent that is currently available for the management of certain cases of hypophosphatasia.

SUN-334 Real-World Clinical Profiles of Adults with Hypophosphatasia (HPP) from the Global HPP Registry

Hypophosphatasia (HPP) is a rare, inherited, metabolic disease caused by low activity of tissue non-specific alkaline phosphatase (TNSALP). HPP in adults has a heterogeneous clinical presentation, often with multiple musculoskeletal and systemic manifestations, which can lead to misdiagnosis and substantial delays in diagnosis. To better understand the most common clinical profile of adults with HPP, data from 270 adults with confirmed HPP diagnosis (≥18 year of age, low ALP and/or ALPL mutation) in the Global HPP Registry were analyzed. Most were women (75.2%) with a median age at enrollment into the registry of 50 years and a median ALP activity of 25 U/L (normal range: 40-150 U/L). Based on medical history, pain (74.8%), mostly described as chronic bone pain or generalized body pain, was the leading symptom reported. Dental manifestations, such as early loss of primary teeth, were reported in 60.4% of adults. Skeletal manifestations, such as recurrent and poorly healing fractures or pseudofractures, were observed in 47.8% of adults. A substantial proportion also reported fatigue (35.2%) and muscle weakness (26.3%). Of the adults who had quality of life data available, median (range) of SF-36v2 Physical Component Score was 42.4 (17.9, 63.3; n=203; population norm=50) and pain interference on the BPI-SF was 3.5 (0, 9.5; n=196; 0=does not interfere; 10=completely interferes). Most adults with available data (n=212) reported some disability on the HAQ-DI (66%). Of these 270 adults, 77 were treated with enzyme replacement therapy (asfotase alfa) while 193 had never received treatment. Demographics and baseline ALP activity were similar between ever and never treated adults. Treated patients had a higher occurrence of pain, dental issues, recurrent and poorly healing fractures or pseudofractures, fatigue, and muscle weakness compared with untreated patients. Generally, treated adults reported poorer quality of life before treatment initiation compared with untreated adults, though data were limited in treated adults. Of the patients treated, 61.0% had pediatric-onset HPP which likely reflects the indication for asfotase alfa in most countries; 29.9% had unknown onset. 57.5% of untreated adults had adult-onset HPP, 24.3% had pediatric-onset, and 18.1% has unknown onset. Pain, dental issues, fatigue, recurrent and poorly healing fractures or pseudofractures, and muscle weakness were the most frequently reported symptoms in both adults with pediatric- or adult-onset HPP. These results establish real-world clinical profiles of adults with HPP, both untreated and before treatment start. Similarities in clinical profiles between adults with pediatric-onset and adult-onset HPP suggest that the age at onset itself is of limited clinical utility; current clinical status and the degree of disability are likely more meaningful in making treatment decisions.