Familial Isolated Hyperparathyroidism Research Articles

FRI692 Severe Hyperparathyroidism And Nephrolithiasis In An Adolescent Male Due To CDC73 Positive Parathyroid Carcinoma

Abstract Disclosure: J.T. Nguyen: None. D.H. Geller: None. A. Ryabets-Lienhard: None. Introduction: Parathyroid carcinoma is a rare cause of primary hyperparathyroidism in the pediatric population, with only 20 previously reported cases. Variations in the CDC73 gene have been associated with sporadic parathyroid carcinoma, autosomal dominant hyperparathyroidism-jaw tumor syndrome (HPT-JT), and familial isolated hyperparathyroidism (FIHP). To our knowledge, only 3 cases of pediatric parathyroid carcinoma with confirmed variants of CDC73 have been reported. We present a case of severe hyperparathyroidism and nephrolithiasis due to parathyroid carcinoma caused by a pathogenic variant in CDC73 in a pediatric patient, highlighting the importance of early recognition and management. Clinical Case: An otherwise asymptomatic 14-year-old male presented with one year of recurrent nephrolithiasis. Initial tests demonstrated hypercalcemia (13.8 mg/dL, 8.4-10.2 mg/dL), normal phosphorous, elevated PTH (1,379 pg/mL, 7.5-53.5 pg/mL), and elevated alkaline phosphatase (514 U/L, 30-250 U/L). The hypercalcemia was treated with hyperhydration, furosemide, and pamidronate. Sestamibi scan revealed a focus of abnormal uptake suggestive of a left parathyroid mass, with ultrasonographic demonstration of a predominantly solid, hypoechoic, and vascular mass centered posterior to the inferior left thyroid lobe. Skeletal survey was notable for trabecular abnormalities and osteopenia. He underwent a left parathyroid mass excision. Final pathology confirmed the parathyroid carcinoma, with multiple foci of vascular invasion without evidence of capsular involvement. Immunohistochemistry demonstrated diffuse positivity for PTH and loss of parafibromin expression by the tumor cells. Genetic testing revealed a pathogenic germline heterozygous nonsense variant in CDC73 (c.376C>T(p.Arg126Ter)) resulting in protein truncation. Post-operative PTH was undetectable with normal calcium and phosphorous. Calcitriol, cholecalciferol, and calcium carbonate supplementation were implemented to prevent further hypocalcemia due to transient hypoparathyroidism and hungry bone syndrome. Calcium supplementation was discontinued within one year of his surgery. Serial thyroid ultrasounds and CT scans have been negative for recurrent or residual disease without evidence of metastasis. Mandibular x-ray showed no evidence of tumors or lesions involving the jaw. He has been noted to have small right renal cysts without other kidney abnormalities. Conclusion: Severe hyperparathyroidism due to parathyroid carcinoma can present as recurrent nephrolithiasis in an otherwise asymptomatic individual. Pediatric patients with a longstanding history of kidney stones should undergo screening for hypercalcemia and hyperparathyroidism even in the absence of other signs and symptoms of elevated calcium to ensure timely diagnosis and appropriate management. Presentation: Friday, June 16, 2023

Novel Glial Cells Missing-2 (GCM2) variants in parathyroid disorders.

ObjectiveThe aim of this study was to analyze variants of the gene glial cells missing-2 (GCM2), encoding a parathyroid cell-specific transcription factor, in familial hypoparathyroidism and in familial isolated hyperparathyroidism (FIHP) without and with parathyroid carcinoma.DesignWe characterized 2 families with hypoparathyroidism and 19 with FIHP in which we examined the mechanism of action of GCM2 variants.MethodsLeukocyte DNA of hypoparathyroid individuals was Sanger sequenced for CASR, PTH, GNA11 and GCM2 mutations. DNA of hyperparathyroid individuals underwent MEN1, CDKN1B, CDC73, CASR, RET and GCM2 sequencing. The actions of identified GCM2 variants were evaluated by in vitro functional analyses.ResultsA novel homozygous p.R67C GCM2 mutation which failed to stimulate transcriptional activity in a luciferase assay was identified in affected members of two hypoparathyroid families. Oligonucleotide pull-down assay and in silico structural modeling indicated that this mutant had lost the ability to bind the consensus GCM recognition sequence of DNA. Two novel (p.I383M and p.T386S) and one previously reported (p.Y394S) heterozygous GCM2 variants that lie within a C-terminal conserved inhibitory domain were identified in three affected individuals of the hyperparathyroid families. One family member, heterozygous for p.I138M, had parathyroid carcinoma (PC), and a heterozygous p.V382M variant was found in another patient affected by sporadic PC. These variants exerted significantly enhanced in vitrotranscriptional activity, including increased stimulation of the PTH promoter.ConclusionsWe provide evidence that two novel GCM2 R67C inactivating mutations with an inability to bind DNA are causative of hypoparathyroidism. Additionally, we provide evidence that two novel GCM2 variants increased transactivation of the PTH promoter in vitro and are associated with FIHP. Furthermore, our studies suggest that activating GCM2 variants may contribute to facilitating more aggressive parathyroid disease.

Do Patients With Atypical Parathyroid Adenoma Need Close Follow-up?

Atypical parathyroid adenomas (APAs) are neoplasms with uncertain malignant potential but lack unequivocal histological signs of malignancy. This work aims to retrospectively evaluate the clinical and biochemical profiles of patients with APA, the outcome after parathyroidectomy (PTX), and the presence of CDC73 germline and somatic mutations. This monocentric study was conducted on consecutive patients undergoing PTX for primary hyperparathyroidism (PHPT) between June 2000 and December 2020. Fifty-eight patients with a confirmed histopathological diagnosis of APA, and age- and sex-matched controls with parathyroid adenoma (PA) were also included. Fifty-four patients had sporadic PHPT and 4 had familial isolated hyperparathyroidism (FIHP). Thirty-four patients (59%) had symptomatic disease. Serum calcium and parathyroid hormone (PTH) levels were significantly higher in symptomatic compared to asymptomatic patients (P = .048 and .008, respectively). FIHP patients were younger than their sporadic counterparts (30 ± 17 years vs 55 ± 13 years). APA patients had significantly higher serum calcium and PTH levels and lower 25-hydroxyvitamin D concentration, bone mineral density, and T score at one-third distal radius compared to those with PA. Four of 56 APA patients displayed a CDC73 germline mutation. No somatic CDC73 mutation was identified in 24 tumor specimens. The mean follow-up after surgery was 60 ± 56.4 months. All but 6 patients (90%), 5 with apparently sporadic PHPT and 1 with FIHP, were cured after surgery. The large majority of patients with APA, despite a moderate/severe phenotype, have a good prognosis. Germline CDC73 mutation-positive patients had a higher rate of persistent/recurrent disease. CDC73 gene alterations do not seem to have a relevant role in the tumorigenesis of sporadic APA.

Abstract #1004047: A Young Patient Presenting with Bone Pain from Brown Tumors due to Underlying Primary Hyperparathyroidism

Brown tumors are focal bone lesions formed by osteoclast and fibroblast proliferation with hemosiderin accumulation causing the brown color. They occur in 3% of secondary hyperparathyroidism and 2% of primary hyperparathyroidism (PHPT). In young patients with PHPT, it is prudent to obtain a thorough family history and consider genetic testing for multiple endocrine neoplasias (MEN), hyperparathyroid-jaw tumor (HPT-JT) syndrome, and familial isolated hyperparathyroidism (FIHP), since preferred surgical management may differ. We present a young man with bone pain who was found to have brown tumors caused by PHPT with negative genetic testing.

Challenges in the differential diagnosis of multiple endocrine neoplasia syndrome type 1 with isolated family hyperparathyroidism

Multiple endocrine neoplasia type 1 (MEN-1) is the most common cause of the hereditary type of primary hyperparathyroidism (PHPT). If a family type of PHPT is suspected, a dynamic monitoring of patients and their close relatives should be carried out throughout their lives. We present a clinical case of a family in which four members of a pedigree were diagnosed with familial isolated hyperparathyroidism (FIHP). The diagnosis was changed to MEN-1, because it appeared that one of the patients had pancreatic neuroendocrine tumor. Molecular genetic study of MEN1 by direct by means of Sanger sequencing revealed that six family members had a new heterozygous mutation in exon 9: s. 1252 G> T p. D418Y.

SAT-370 Novel CASR Gene Mutation as a Cause of Familial Isolated Primary Hyperparathyroidism

BACKGROUND: Primary hyperparathyroidism (pHT) is one of the most common causes of hypercalcemia. About 10% of these patients have a familial cause of which MEN and the hyperparathyroid-jaw tumor syndrome (HJTs) are most common. Familial hypocalciuric hypercalcemia (FHH) due to loss of function mutations of the calcium sensing receptor (CASR) gene is an important familial mimic of this that needs to be distinguished. Beyond this are still a group of patients with familial isolated primary hyperparathyroidism (FIpHT). Recognition of this entity is important because of the different prognostic and surgical treatment strategy for their management compared to regular sporadic pHT. Clinical Case: A 58 yr old postmenopausal lady on topical HRT was referred for thyroid nodular disease. Her initial lab tests showed primary hyperparathyroidism with mild hypercalcemia. Her initial neck sonogram showed multiple benign appearing nodules that did not warrant biopsy. There was a history of hypothyroidism in her mother and thyroid cancer in a maternal cousin. In addition, her father and two sons have history of hypercalcemia that required repeated hospital admissions for treatment. Her two daughters to date have had no hypercalcemia, nephrolithiasis nor thyroid problems. There was no family history of jaw, renal nor brain or pituitary tumors and no history of severe dyspeptic disease nor familial cancers. She had hypercalciuria, normal bone density and non-obstructive nephrolithiasis. MEN-1 gene testing was normal. Parathyroid scan suggested a possible right sided parathyroid lesion and she had elective parathyroidectomy of an ectopic right parathyroid that was hypercellular on histology. The intra-operative PTH dropped following the lesion extraction by ~ 51%. Post operatively the patient’s mild pHT and hypercalcemia persists but imaging studies have been unrevealing. Further genetic testing for other possible etiologies of familial pHT were -ve for HJTs but revealed a novel somatic mutation of the CASR gene; c.1868G>A (p.Gly623Asp) whose present significance is unclear. This variant has been described in one family with FHH but In silico predictive analyses of the mutation suggests a possible deleterious effect. Given her known family history of symptomatic hypercalcemia this novel mutation appears to be a hitherto unrecognized cause for FIpHT. The patient is presently being conservatively managed and monitored. Conclusion: While familial pHT is relatively uncommon its recognition is important as it can inform planned surgical intervention and expected prognosis for anticipated cure. While MEN and HJTs are the most common etiologies for familial pHT other possibilities need to considered when the history suggests possible FIpHT and our case highlights a novel CASR mutation as diagnostic consideration.

GCM2 variant - A rare genetic cause of Familial Isolated Hyperparathyroidism

GCM2 variant - A rare genetic cause of Familial Isolated Hyperparathyroidism

Whole exome sequencing in familial isolated primary hyperparathyroidism.

Familial isolated hyperparathyroidism (FIHP) is a rare inherited disease accounting for 1% of all cases of primary hyperparathyroidism (PHPT). It is genetically heterogeneous being associated with mutations in different genes, including MEN1, CDC73, CASR, and recently GCM2. The aim of the study was to further investigate the molecular pathogenesis in Italian FIHP kindreds. We used whole exome sequencing (WES) in the probands of seven unrelated FIHP kindreds. We carried out a separate family-based exome analysis in a large family characterized by the co-occurrence of PHPT with multiple tumors apparently unrelated to the disease. Selected variants were also screened in 18 additional FIHP kindreds. The clinical, biochemical, and pathological characteristics of the families were also investigated. Three different variants in GCM2 gene were found in two families, but only one (p.Tyr394Ser), already been shown to be pathogenic in vitro, segregated with the disease. Six probands carried seven heterozygous missense mutations segregating with the disease in the FAT3, PARK2, HDAC4, ITPR2 and TBCE genes. A genetic variant in the APC gene co-segregating with PHPT (p.Val530Ala) was detected in a family whose affected relatives had additional tumors, including colonic polyposis. We confirm the role of GCM2 germline mutations in the pathogenesis of FIHP, although at a lower rate than in the previous WES study. Further studies are needed to establish the prevalence and the role in the predisposition to FIHP of the novel variants in additional genes.

MON-319 A Young Woman with Familial Isolated Primary Hyperparathyroidism Due to Parathyroid Adenoma and Atrophic Gastritis

Background: High levels of gastrin and parathyroid hormone (PTH) can coexist outside the multiple endocrine neoplasia (MEN) kindred syndromes. There is significant non-causal association between chronic autoimmune atrophic gastritis (CAAG) and primary hyperparathyroidism (PHPT). Prevalence of PHPT is increased in patients with CAAG (8.4 vs 1–3%, general population).1,2 These studies excluded people with familial PHPT, MEN1 syndrome, those on proton pump inhibitors, H. pylori infection and renal failure. Some studies show an association between gastric carcinoid type 1 tumor (GC-1) and PHPT.3 No data is available on association between hypergastrinemia, gastritis and familial isolated HPT (FIHPT) Case: A 37-year-old female with hypothyroidism due to Hashimoto’s thyroiditis and premature ovarian insufficiency was incidentally found to have hypercalcemia with total calcium of 10.8 mg/dL (8.9–10.4), ionized calcium 1.4 mg/dL (1.14–1.33), 24 hour urine calcium of 0.252 g/d (0.032–0.368), urine creatinine 0.56 g/24hr (0.78–2.31), urine volume 1650 mL. 25 OH Vitamin D was low at 17 pg/ml. She also had elevated chromogranin A level at 541 ng/mL (0–95), gastrin level of 1522 pg/mL (0–100) and Vitamin B12 level of 299 pg/mL (> 201 acceptable), negative intrinsic factor and antiovarian antibody. There is a strong family history of primary hyperparathyroidism in mother and sister and hypercalcemia in brother and niece (unknown workup). Parathyroid scan showed ectopic parathyroid adenoma, with mild focal uptake a few centimeters inferior to the lower pole of the right thyroid gland. Bone density scan showed osteopenia at L1- L4 lumbar spine with T score -2.1 and BMD of 0.924 g/cm2. Genetic test was negative for CASR, CDC73, CDKN1B, MEN1, RET amplified by long-range PCR and sequenced by Pacific Biosciences SMRT. Upper GI endoscopy with gastric biopsy showed severe chronic atrophic gastritis with extensive intestinal metaplasia associated with diffuse neuroendocrine cell hyperplasia within the crypts. She was diagnosed with familial isolated primary hyperparathyroidism with chronic atrophic gastritis. Conclusion: As far as we know, there are no reported cases documenting chronic atrophic gastritis occurring with familial isolated primary hyperparathyroidism. This case highlights that in patients with FIHPT, hypergastrinemia and gastritis can occur independent of MEN -1 syndrome.

New Concepts About Familial Isolated Hyperparathyroidism.

Familial isolated hyperparathyroidism (FIHP) is defined as familial primary hyperparathyroidism (FH) without a characteristic extraparathyroidal feature of a more complex hyperparathyroid syndrome. New concepts of FIHP have been developed within this definition. FIHP has been difficult to study due to small kindreds and mildly symptomatic cases. Searches were through PubMed for FIHP, other FH syndromes, and the gene(s) mutated in each. Within its definition, the current concept of FIHP has clinical and mutational components that can include incomplete expressions of multiple endocrine neoplasia type 1 (MEN1) familial hypocalciuric hypercalcemia, hyperparathyroidism-jaw tumor syndromes, or their mutations. Newest concepts of FIHP focus on kindreds without mutation of the MEN1, CASR, or CDC73 genes; 17% have germline activating mutation of the gene for the GCM2 transcription factor. The FIHP kindreds with or without GCM2 mutation contain a median of only two cases of primary hyperparathyroidism. The small kindred size in both subgroups of FIHP is probably caused by a low rate of screening among relatives. Persons with FIHP and GCM2 mutation present as adults with mild hypercalcemia and multiple parathyroid tumors. The current concept of FIHP led to a focus on small kindreds without mutation of MEN1, CASR, or CDC73. These assisted in identifying germline activating GCM2 mutations in 17% of kindreds. Clinical and mutational characterization in more cases is needed to determine if there are any unique clinical features of FIHP, with or without mutation of GCM2.

Hereditary forms of primary hyperparathyroidism

Primary hyperparathyroidism (PHPT) is sporadic in the majority of cases. Hereditary forms of PHPT are rarer, however, they are of particular interest because they allow a deeper understanding of pathogenesis of parathyroid neoplasia. Hereditary forms of PHPT include multiple endocrine neoplasia type 1 (MEN-1), type 2A (MEN-2A), type 4 (MEN-4), hyperparathyroidism-jaw tumour syndrome (HPT-JT), variants of familial hypocalciuric hypercalcemia (FHH) and familial isolated hyperparathyroidism (FIHP). Mutations in the following genes cause the development of MEN-1, MEN-2A, MEN4, HPT-JT: MEN1, RET, CDKN1B, CDC73, respectively. Variants of FHH are caused by mutations in CASR, AP2S1, GNA11. Gene(s) responsible for the development of the majority of FIHP cases remain unknown.
 Identification of hereditary forms of PHPT is important for patients and their first-degree relatives, as it allows defining the necessity of screening to reveal other components of the syndrome, in some cases determines the surgical approach to PHPT, and the risk of development of the disease in offsprings.
 This article provides information on hereditary syndromes associated with PHPT and special features of PHPT in each syndrome.

Mutational and large deletion study of genes implicated in hereditary forms of primary hyperparathyroidism and correlation with clinical features.

The aim of this study was to carry out genetic screening of the MEN1, CDKN1B and AIP genes, both by direct sequencing of the coding region and multiplex ligation-dependent probe amplification (MLPA) assay in the largest monocentric series of Italian patients with Multiple Endocrine Neoplasia type 1 syndrome (MEN1) and Familial Isolated Hyperparathyroidism (FIHP). The study also aimed to describe and compare the clinical features of MEN1 mutation-negative and mutation-positive patients during long-term follow-up and to correlate the specific types and locations of MEN1 gene mutations with onset and aggressiveness of the main MEN1 manifestations. A total of 69 index cases followed at the Endocrinology Unit in Pisa over a period of 19 years, including 54 MEN1 and 15 FIHP kindreds were enrolled. Seven index cases with MEN1 but MEN1 mutation-negative, followed at the University Hospital of Cagliari, were also investigated. FIHP were also tested for CDC73 and CaSR gene alterations. MEN1 germline mutations were identified in 90% of the index cases of familial MEN1 (F-MEN1) and in 23% of sporadic cases (S-MEN1). MEN1 and CDC73 mutations accounted for 13% and 7% of the FIHP cohort, respectively. A CDKN1B mutation was identified in one F-MEN1. Two AIP variants of unknown significance were detected in two MEN1-negative S-MEN1. A MEN1 positive test best predicted the onset of all three major MEN1-related manifestations or parathyroid and gastro-entero-pancreatic tumors during follow-up. A comparison between the clinical characteristics of F and S-MEN1 showed a higher prevalence of a single parathyroid disease and pituitary tumors in sporadic compared to familial MEN1 patients. No significant correlation was found between the type and location of MEN1 mutations and the clinical phenotype. Since all MEN1 mutation-positive sporadic patients had a phenotype resembling that of familial MEN1 (multiglandular parathyroid hyperplasia, a prevalence of gastro-entero-pancreatic tumors and/or the classic triad) we might hypothesize that a subset of the sporadic MEN1 mutation-negative patients could represent an incidental coexistence of sporadic primary hyperparathyroidism and pituitary tumors or a MEN1 phenocopy, in our cohort, as in most cases described in the literature.

Large intragenic deletion of CDC73 (exons 4\u201310) in a three-generation hyperparathyroidism-jaw tumor (HPT-JT) syndrome family

BackgroundInactivating mutations of CDC73 cause Hyperparathyroidism-Jaw Tumour syndrome (HPT-JT), Familial Isolated Hyperparathyroidism (FIHP) and sporadic parathyroid carcinoma. We conducted CDC73 mutation analysis in an HPT-JT family and confirm carrier status of the proband’s daughter.MethodsThe proband had primary hyperparathyroidism (parathyroid carcinoma) and uterine leiomyomata. Her father and daughter had hyperparathyroidism (parathyroid adenoma) but no other manifestations of HPT-JT. CDC73 mutation analysis (sequencing of all 17 exons) and whole-genome copy number variation (CNV) analysis was done on leukocyte DNA of the three affecteds as well as the proband’s unaffected sister.ResultsA novel deletion of exons 4 to 10 of CDC73 was detected by CNV analysis in the three affecteds. A novel insertion in the 5’UTR (c.-4_-11insG) that co-segregated with the deletion was identified. By in vitro assay the 5’UTR insertion was shown to significantly impair the expression of the parafibromin protein. Screening for the mutated CDC73 confirmed carrier status in the proband’s daughter and the biochemistry and ultrasonography led to pre-emptive surgery and resolution of the hyperparathyroidism.ConclusionsA novel gross deletion mutation in CDC73 was identified in a three-generation HPT-JT family emphasizing the importance of including screening for large deletions in the molecular diagnostic protocol.

Abstract 5646: Germline activating mutations in the proto-oncogene GCM2 in primary hyperparathyroidism

Abstract Primary hyperparathyroidism (PHPT) is a common endocrine disease caused by parathyroid tumors (adenoma or hyperplasia). The hypersecreting parathyroid tumor elevates serum parathyroid hormone level, which causes hypercalcemia and the classical symptoms of PHPT, including kidney stones, osteoporosis, and neuromuscular symptoms associated with hypercalcemia, such as muscle weakness, drowsiness, and depression. Familial PHPT occurs in an isolated nonsyndromal form, termed familial isolated hyperparathyroidism (FIHP), or as part of a syndrome, such as multiple endocrine neoplasia type 1 or hyperparathyroidism-jaw tumor syndrome. We performed exome sequencing on germline DNA of eight index cases from eight unrelated kindreds with FIHP. Rare variants were identified (minor allele frequency <1%), and selected variants were assessed for co-segregation in affected family members by Sanger sequencing. Candidate genes were then screened in an additional 32 kindreds with FIHP. The functional consequence of variants in one FIHP candidate gene (GCM2, a parathyroid tissue-specific transcription factor) was analyzed in a cell culture model. In eight kindreds with FIHP, we identified three rare GCM2 missense variants. Functional characterization of GCM2 variants and deletion-analyses revealed a small C-terminal Conserved Inhibitory Domain (CCID). Two of the three rare variants were recurrent, located in the CCID that enhanced the transcriptional activity of GCM2, and found in seven of 40 (18%) kindreds with FIHP. Functional assays for transcriptional activity demonstrated that these two rare variants acted as gain-of-function mutations, suggesting that GCM2 is a parathyroid proto-oncogene. We further investigated the ethnicity of individuals with GCM2 CCID activating variants in PHPT patient samples and in genome survey datasets. Our results demonstrate that germline activating mutations in the GCM2 CCID can cause FIHP, and specific activating mutations expose a large population at risk for PHPT. Our findings of the first gene with mutations specific for FIHP are expected to have an important impact on clinical practice, including treatment decisions and genetic testing of individuals with PHPT and family members. Citation Format: Bin Guan, James M. Welch, Julie C. Sapp, Hua Ling, Meghana Vemulapalli, Yulong Li, Jennifer J. Johnston, Electron Kebebew, Leslie G. Biesecker, William F. Simonds, Stephen J. Marx, Sunita K. Agarwal. Germline activating mutations in the proto-oncogene GCM2 in primary hyperparathyroidism [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5646. doi:10.1158/1538-7445.AM2017-5646

Ethnicity of Patients With Germline GCM2-Activating Variants and Primary Hyperparathyroidism.

Context:Germline gain-of-function variants in the transcription factor GCM2 were found in 18% of kindreds with familial isolated hyperparathyroidism (FIHP). These variants [c.1136T>A (p.Leu379Gln) and c.1181A>C (p.Tyr394Ser)] were located in a 17-amino acid transcriptional inhibitory domain named C-terminal conserved inhibitory domain (CCID).Objective:We investigated the ethnicity of individuals with germline variants in the GCM2 CCID in our primary hyperparathyroidism (PHPT) patient samples and in the Genome Aggregation Database.Design:Ethnicity information was obtained from an in-house clinical database and genetic counseling. Sanger sequencing of blood DNA was used to determine the genotype of the GCM2 CCID region. Luciferase reporter assays were performed to determine the functional impact of GCM2 variants.Setting and Patients:National Institute of Diabetes and Digestive and Kidney Diseases endocrine clinic is a service that accepts PHPT referral patients.Results:The GCM2 p.Tyr394Ser variant was found in 41% [95% confidence interval (CI), 22% to 64%] of Ashkenazi Jewish (AJ) kindreds with FIHP and in 27% (95% CI, 17% to 40%) of AJ patients with sporadic PHPT. The p.Tyr394Ser variant was also found in sporadic PHPT patients of European ancestry, but at a lower prevalence. The p.Leu379Gln variant was found in 8% (95% CI, 1% to 26%) of European kindreds with FIHP and 0.5% (95% CI, 0% to 3.0%) of sporadic PHPT cases of European ancestry. The sporadic PHPT patients with GCM2-activating variants often had multigland involvement or postoperative recurrent or persistent disease.Conclusions:Specific GCM2-activating variants enriched among various ethnic backgrounds could contribute to a large number of cases with FIHP or sporadic PHPT.

GCM2-Activating Mutations in Familial Isolated Hyperparathyroidism

Primary hyperparathyroidism (PHPT) is a common endocrine disease characterized by parathyroid hormone excess and hypercalcemia and caused by hypersecreting parathyroid glands. Familial PHPT occurs in an isolated nonsyndromal form, termed familial isolated hyperparathyroidism (FIHP), or as part of a syndrome, such as multiple endocrine neoplasia type 1 or hyperparathyroidism-jaw tumor syndrome. The specific genetic or other cause(s) of FIHP are unknown. We performed exome sequencing on germline DNA of eight index-case individuals from eight unrelated kindreds with FIHP. Selected rare variants were assessed for co-segregation in affected family members and screened for in an additional 32 kindreds with FIHP. In eight kindreds with FIHP, we identified three rare missense variants in GCM2, a gene encoding a transcription factor required for parathyroid development. Functional characterization of the GCM2 variants and deletion analyses revealed a small C-terminal conserved inhibitory domain (CCID) in GCM2. Two of the three rare variants were recurrent, located in the GCM2 CCID, and found in seven of the 40 (18%) kindreds with FIHP. These two rare variants acted as gain-of-function mutations that increased the transcriptional activity of GCM2, suggesting that GCM2 is a parathyroid proto-oncogene. Our results demonstrate that germline-activating mutations affecting the CCID of GCM2 can cause FIHP.

Molecular and genetic features of primary hyperparathyroidism in young patients

When primary hyperparathyroidism (PHPT) is diagnosed in a young patient in the absence of other clinical manifestations differential diagnosis between a sporadic form of PHPT and PHPT as the first manifestation of one of hereditary syndromes may be challenging. Diagnosis of sporadic or hereditary PHPT determines the extent of surgical intervention, a strategy for further observation and treatment, and the need for examination and treatment of first-degree relatives. Aim of the study — to determine genetic characteristics of PHPT with manifestation at a young age (<40 years old) with clinically sporadic PHPT and familial isolated hyperparathyroidism (FIHP).Material and methods. 40 patients with manifestation of PHPT at the age younger than 40 years, 4 of which with FIHP, were included in the study. In 11 patients Sanger sequencing of MEN1 gene was performed (ABI 3130 Genetic Analyser, «Applied Biosystems», USA). 37 patients underwent next-generation sequencing (NGS) (Ion Torrent PGM, Thermo Fisher Scientific — Life Technologies, USA) using a panel of candidate genes (MEN1, CASR, CDC73, CDKN1A, CDKN1B, CDKN1C, CDKN2A, CDKN2C, CDKN2D). Results. In 3 (7,5%) patients (1 of which with FIHP) we revealed germline heterozygous mutations in MEN1 gene: in exon 9 p.D418N, exon 3 p.R176Q, intron 3 с.654+1G>A. In 4 (4/40, 10%) patients we revealed germline heterozygous mutations in CDC73 gene: 3 nonsense mutations in patients with parathyroid carcinoma — in exon 3 p.R91X, exon 6 p.Q166X, exon 7 p.R229X, and 1 missense mutation in a patient with parathyroid hyperplasia in exon 8 p.R263C. Conclusions. In the majority of cases (75%) PHPT in young patients without positive family history is sporadic. Search for germline mutations in the genes, leading to development of hereditary forms of PHPT (first of all in MEN1 and CDC73), is appropriate in young patients with positive family history, or when positive family history may be suspected, and in patients with parathyroid carcinoma. In the majority (75%) of FIHP cases search for other, probably yet unknown, genes is necessary.

Hereditary hyperparathyroidism--a consensus report of the European Society of Endocrine Surgeons (ESES).

Hereditary hyperparathyroidism has been reported to occur in 5-10 % of cases of primary hyperparathyroidism in the context of multiple endocrine neoplasia (MEN) types 1, 2A and 4; hyperparathyroidism-jaw tumour (HPT-JT); familial isolated hyperparathyroidism (FIHPT); familial hypocalciuric hypercalcaemia (FHH); neonatal severe hyperparathyroidism (NSHPT) and autosomal dominant moderate hyperparathyroidism (ADMH). This paper aims to review the controversies in the main genetic, clinical and pathological features and surgical management of hereditary hyperparathyroidism. A peer review literature analysis on hereditary hyperparathyroidism was carried out and analyzed in an evidence-based perspective. Results were discussed at the 2015 Workshop of the European Society of Endocrine Surgeons devoted to hyperparathyroidism due to multiple gland disease. Literature reports scarcity of prospective randomized studies; thus, a low level of evidence may be achieved. Hereditary hyperparathyroidism typically presents at an earlier age than the sporadic variants. Gene penetrance and expressivity varies. Parathyroid multiple gland involvement is common, but in some variants, it may occur metachronously often with long disease-free intervals, simulating a single-gland involvement. Bilateral neck exploration with subtotal parathyroidectomy or total parathyroidectomy + autotransplantation should be performed, especially in MEN 1, in order to decrease the persistent and recurrent hyperparathyroidism rates; in some variants (MEN 2A, HPT-JT), limited parathyroidectomy can achieve long-term normocalcemia. In FHH, surgery is contraindicated; in NSHPT, urgent total parathyroidectomy is required. In FIHPT, MEN 4 and ADMH, a tailored case-specific approach is recommended.

CDC73 intragenic deletion in familial primary hyperparathyroidism associated with parathyroid carcinoma.

Context:CDC73 mutations frequently underlie the hyperparathyroidism-jaw tumor syndrome, familial isolated hyperparathyroidism (FIHP), and parathyroid carcinoma. It has also been suggested that CDC73 deletion analysis should be performed in those patients without CDC73 mutations.Objective:To investigate for CDC73 deletion in a family with FIHP previously reported not to have CDC73 mutations.Patients and Methods:Eleven members (six affected with primary hyperparathyroidism and five unaffected) were ascertained from the family, and multiplex ligation-dependent probe amplification was performed to detect CDC73 deletion using leukocyte DNA.Results:A previously unreported deletion of CDC73 involving exons 1–10 was detected in five affected members and two unaffected members who were 26 and 39 years of age. Two affected members had parathyroid carcinomas at the ages of 18 and 32 years, and they had Ki-67 proliferation indices of 5 and 14.5% and did not express parafibromin, encoded by CDC73. Primary hyperparathyroidism in the other affected members was due to adenomas and atypical adenomas, and none had jaw tumors. Two affected members had thoracic aortic aneurysms, which in one member occurred with parathyroid carcinoma and renal cysts.Conclusion:A previously unreported intragenic deletion of exons 1 to 10 of CDC73 was detected in a three-generation family with FIHP, due to adenomas, atypical adenomas, and parathyroid carcinomas. In addition, two affected males had thoracic aortic aneurysms, which may represent another associated clinical feature of this disorder.

Genetic basis of familial isolated hyperparathyroidism: a case series and a narrative review of the literature

Primary hyperparathyroidism is a heterogeneous clinical entity. In the clinical setting, the diagnosis and management of familial isolated hyperparathyroidism (FIHP) and other familial hyperparathyroidism (FHPT) forms continue to rely on clinical, laboratory, and histological findings, with careful examination of the family. In this article, we report a case series of FIHP in a four-generation Greek family, with no identifiable gene mutations. Clinical approach and long-term follow-up are discussed and a narrative review of the genetic basis of this entity has been performed.