Cases Of Osteogenesis Imperfecta Research Articles

Exome Sequencing for the Diagnostics of Osteogenesis Imperfecta in Six Russian Patients.

Osteogenesis imperfecta (OI) is a group of inherited disorders of connective tissue that cause significant deformities and fragility in bones. Most cases of OI are associated with pathogenic variants in collagen type I genes and are characterized by pronounced polymorphisms in clinical manifestations and the absence of clear phenotype-genotype correlation. The objective of this study was to conduct a comprehensive molecular-genetic and clinical analysis to verify the diagnosis of OI in six Russian patients with genetic variants in the COL1A1 and COL1A2 genes. Clinical and laboratory data were obtained from six OI patients who were observed at the Medical Genetics Center in Saint Petersburg from 2016 to 2023. Next-generation sequencing on MGISEQ G400 (MGI, China) was used for DNA analysis. The GATK bioinformatic software (version 4.5.0.0) was used for variant calling and hard filtering. Genetic variants were verified by the direct automatic sequencing of PCR products using the ABI 3500X sequencer. We identified six genetic variants, as follows pathogenic c.3505G>A (p. Gly1169Ser), c.769G>A (p.Gly257Arg), VUS c.4123G>A (p.Ala1375Thr), and c.4114A>T (p.Asn1372Tyr) in COL1A1; and likely pathogenic c.2035G>A (p.Gly679Ser) and c.739-2A>T in COL1A2. In addition, clinical cases are presented due to the presence of the c.4114A>T variant in the COL1A2 gene. Molecular genetics is essential for determining different OI types due to the high similarity across various types of the disease and the failure of unambiguous diagnosis based on clinical manifestations alone. Considering the variable approaches to OI classification, an integrated strategy is required for optimal patient management.

A Retrospective Study of the Presentation, Diagnosis, Management, and Outcomes of 27 Patients with Osteogenesis Imperfecta at a Single Center in Türkiye.

BACKGROUND This retrospective study aimed to evaluate the presentation, diagnosis, management, and outcomes of 27 patients diagnosed with osteogenesis imperfecta at a single center in Türkiye between January 2011 and January 2020. MATERIAL AND METHODS We analyzed data from the medical records of 27 patients with osteogenesis imperfecta admitted to Çukurova University Faculty of Medicine, Department of Orthopedics and Traumatology, between January 2011 and January 2020. The data included the clinical examination notes of the cases classified according to the Sillence and Shapiro systems, age, sex, parental consanguinity, genetic analysis (DNA isolation) results, the number and localization of past fractures, treatment methods, complications, hypermobility, and ambulation scoring. RESULTS The mean age of the patients (n=13 male, n=14 female) was 10.4±7.4 years, ranging from 3 to 39 years. Almost half (n=15, 55.6%) had consanguineous parents. The patients had 131 fractures during the 9 years between January 2011 and January 2020, with the femur being the most commonly fractured bone; 13 patients (48.15%) received surgical and conservative treatments, while the remaining 14 underwent only conservative treatments. The results revealed a strong association between the number of fractures and the types of genetic mutations (P=0.004). CONCLUSIONS Study findings indicate that the type of genetic mutation was not significantly correlated with the risk of treatment complications in osteogenesis imperfecta cases. Nevertheless, the study reveals a noteworthy association between the type of mutation and the number of surgeries required. Specifically, patients with the COL1A1 mutation needed more surgeries.

Exome sequencing identified mutations in the WNT1 and COL1A2 genes in osteogenesis imperfecta cases.

Osteogenesis imperfecta (OI) is a heritable connective tissue disorder characterized by bone deformities, fractures and reduced bone mass. OI can be inherited as a dominant, recessive, or X-linked disorder. The mutational spectrum has shown that autosomal dominant mutations in the type I collagen-encoding genes are responsible for OI in 85% of the cases. Apart from collagen genes, mutations in more than 20 other genes, such as CRTAP, CREB3L1, MBTPS2, P4HB, SEC24D, SPARC, FKBP10, LEPRE1, PLOD2, PPIB, SERPINF1, SERPINH1, SP7, WNT1, BMP1, TMEM38B, and IFITM5 have been reported in OI. To understand the genetic cause of OI in four cases, we conducted whole exome sequencing, followed by Sanger sequencing. In case #1, we identified a novel c.506delG homozygous mutation in the WNT1 gene, resulting in a frameshift and early truncation of the protein at the 197th amino acid. In cases #2, 3 and 4, we identified a heterozygous c.838G > A mutation in the COL1A2 gene, resulting in a p.Gly280Ser substitution. The clinvar frequency of this mutation is 0.000008 (GnomAD-exomes). This mutation has been identified by other studies as well and appears to be a mutational hot spot. These pathogenic mutations were found to be absent in 96 control samples analyzed for these sites. The presence of these mutations in the cases, their absence in controls, their absence or very low frequency in general population, and their evaluation using various in silico prediction tools suggested their pathogenic nature. Mutations in the WNT1 and COL1A2 genes explain these cases of osteogenesis imperfecta.

Osteogenesis Imperfecta: One Disease, Two or More Faces: A Case Report

Being such a rare condition in paediatrics, osteogenesis imperfecta (OI) is not a diagnosis which is made often. It is however, a diagnosis necessitating early diagnosis and timeous and effective management to improve morbidity and increase the quality of life for our patients. We report two cases of osteogenesis imperfecta in this case report to highlight the different phenotypic presentations. Both of these patients are unique in their presentations and each case highlights the importance of a high clinical index of suspicion by the practitioner in making the diagnosis of osteogenesis imperfecta. The first case is a patient who was diagnosed with osteogenesis imperfecta on day one of life. She had disproportionate short stature, blue sclera, a small chest and bowing of her lower limbs with swellings and tenderness over both of her femurs. A babygram radiograph revealed multiple fractures, with the presence of callus formation at some fracture sites suggesting intrauterine fractures. The second case is a patient who had normal anthropometry and was well at birth. She was subsequently diagnosed at two weeks of age when she presented to the Chris Hani Baragwanath Academic Hospital with an E. coli meningitis and she was suspected to have a right clavicular fracture and possibly rib fractures as she had pain on palpation over these areas. She was noted to have no blue sclera. Subsequent X-rays confirmed a right clavicular fracture as well as left and right rib fractures at different stages of healing. A lateral skull radiograph revealed Wormian bones. With no available genetic testing in South Africa, both diagnoses were made clinically. Both of our patients were started on zoledronic acid at three months of age and were followed up by the Metabolic Unit at the Chis Hani Baragwanath Academic Hospital. This case report of two patients highlights the characteristics important in diagnosing and treating this uncommon condition with varying phenotypical presentations, thus ensuring that the diagnosis is not missed or misdiagnosed: one disorder, two different faces.

Squint surgery in a case of osteogenesis imperfecta

<br>Osteogenesis imperfecta (OI) is well known to be associated with blue sclera due to thinning along with skeletal deformities. Not all cases of OI have blue sclera despite having a thinner sclera than in normal individuals. We are presenting a case report of a 28-year-old girl with intermittent exotropia and OI with no evidence of blue sclera. On AS-OCT, scleral thinning was noted at the level of medial rectus muscle insertion. The patient underwent successful recession-resection surgery for the same. The thin sclera and OI need not deter the decision to operate on squint, and a successful squint surgery is possible in eyes with some amount of scleral thinning with careful suturing.<br>

Lumbar Scheuermann\u2019s disease found in a patient with osteogenesis imperfecta (OI) caused by a heterozygous mutation in COL1A2 (c.4048G\u2009>\u2009A): a case report

BackgroundOsteogenesis imperfecta (OI) is a heterogeneous connective tissue disorder characterized by increased bone fragility and a series of extraskeletal manifestations. Approximately 90 % of OI cases are caused by type I collagen variants encoded by the collagen type I alpha 1 (COL1A1) or type I alpha 2 (COL1A2) gene. Lumbar Scheuermann’s disease is an atypical type of Scheuermann’s disease accompanied by Schmorl’s nodes and irregular endplates but without pronounced kyphosis. Although the etiology of Scheuermann’s disease is unclear, genetic and environmental factors are likely.Case presentationHere, we report a 32-year-old male patient who experienced multiple brittle fractures. Gene sequencing revealed a heterozygous mutation, c.4048G > A (p.G1350S), in the COL1A2 gene, and the patient was diagnosed with OI. Magnetic resonance imaging of his thoracolumbar spine revealed multiple Schmorl’s nodes.ConclusionsThis is the first reported case of OI coexisting with the spinal presentation of Scheuermann’s disease. It is speculated that the COL1A2 gene mutation might be an underlying novel genetic cause of Scheuermann’s disease. In conclusion, this case demonstrates the relationship between Scheuermann’s disease and OI for the first time and enriches the genotype-phenotype spectrum of OI.

Inter- and Intrafamilial Phenotypic Variability in Individuals with Collagen-Related Osteogenesis Imperfecta.

Osteogenesis imperfecta (OI) is a rare genetic disorder also known as a “brittle bone disease.” Around 90% of patients with OI harbor loss‐of‐function or dominant negative pathogenic variants in the COL1A1 and COL1A2 genes, which code for collagen type I α1 and α2 chains. Collagen‐related forms of the disorder are classified as Sillence OI types I–IV. OI phenotype expression ranges from mild to lethal. The current study aims to evaluate associations between interfamilial and intrafamilial phenotypic variability and genotype characteristics of patients with collagen‐related OI. The study was based on a systematic review of collagen‐related OI cases from the University of Tartu OI database (n = 137 individuals from 81 families) and the Dalgleish database (n = 479 individuals). Interfamilial variability analysis has shown that 17.74% of all studied OI‐related variants were associated with the same phenotype. The remaining 82.26% of pathogenic variants were associated with variable phenotypes. Additionally, higher interfamilial variability correlated with the COL1A1 gene (P value = 0.001) and dominant‐negative variants (P value = 0.0007). Within intrafamilial variability, 32.81% families had increasing or decreasing OI phenotype severity across generations. Higher intrafamilial variability of phenotypes correlated with the collagen I dominant negative variants (P value = 0.0246). The current study shows that, in line with other phenotype modification factors, OI interfamilial and intrafamilial diversity potential is associated with the genotype characteristics of the OI‐causing pathogenic variants. The results of the current study may advance knowledge of OI phenotype modification as well as assist family planning and the evaluation of disease progression in subsequent generations.

Quality of Life Evaluation in Children With Osteogenesis Imperfecta After Giving Bisphosphonate Infusion in Dr. Soetomo Hospital Surabaya

INTRODUCTION&#x0D; Osteogenesis imperfecta (OI) or brittle bone disease is a connective tissue formation disorder that is generally characterized by bone fragility, osteopenia, blue sclera, dentinogenesis imperfecta (DI), and hearing loss. Clinical symptoms vary greatly between patients even in the same type. The lack of evaluation of the effect of bisphosphonate on the quality of life of pediatric patients is the main reason for the authors to evaluate the quality of life in pediatric patients with Ostegenesis imperfecta in Soetomo Hospital Surabaya.&#x0D; METHOD&#x0D; The author selected three cases of OI from an outpatient installation of Dr. Soetomo Hospital who was given the management of bisphosphonate administration. Then compared before giving Bisphosphonate and after giving bisphosphonate for 1.5 years and evaluated using the SF36 questionnaire and DASH score.&#x0D; RESULTS&#x0D; In the DASH score assessment, there is no evaluation in the Work Module section (optional) because the patient is still a child. From the results of SF36 evaluation in evaluating the quality of life of patients with Osteogenesis imperfecta in the administration of bisphosphonate, it appears that the development is better compared to before administration of bisphosphonate.&#x0D; DISCUSSION&#x0D; From the evaluation results using the DASH score, all three patients had a good development in terms of motor development in upper extremities. this can be seen from the evaluation of the development of muscle strength and fine motor strength such as writing (drawing), eating his own food without the help of parents and also carrying a heavier burden. It's just that the evaluation of bisphosphonate administration is biased by the motor development of each patient.&#x0D; From the points of Emotional Health and Social Attitude, it can be concluded that patients are bolder to move and move more than before. Before giving bisphosphonate, according to anamnesis from parents, patients are relatively afraid to move, this is due to fear of recurring fractures in patients. After giving bisphosphonate the patient is more willing to move and play with the surrounding environment. From the evaluation of Pain points, there is a significant difference between post and before bisphosphonate administration, this may be due to the reduced frequency of fractures compared to after administration of bisphosphonate.&#x0D; Another important modality in handling OI is rehabilitation of physiotherapy. The goal of rehabilitation in OI patients is primarily to improve joint motion and muscle strength, as well as to improve ambulation and functional ability. OI's condition is chronic and requires lifelong treatment that can reduce children's quality of life. Therefore, in patients with chronic disease conditions that require long-term therapy even for life, it is very important to provide education about understanding children's diseases, the need for lifelong monitoring and treatment, efforts that need to be made to prevent and minimize complications, the importance of the second role parents in providing appropriate parenting, fostering, and fostering for optimal child growth and quality of life&#x0D; CONCLUSION&#x0D; Significant effects were seen after bisphosphonate administration. The need for a thorough evaluation of the effects of bisphosphonate administration on pediatric Osteogenesis Imperfecta patients. The need for a standard and specific questionnaire for the evaluation of the development of bisphosphonate therapy in patients with Osteogenesis Imperfecta.&#x0D; &#x0D;

Osteogenesis imperfecta in a male holstein calf associated with a possible oligogenic origin

Background Neuromusculoskeletal anomalies generally in combination with severe clinical symptoms, comprise a heterogeneous group of fairly common and mostly fatal disorders in man and animals. Osteogenesis imperfecta (OI), also known as brittle bone disease, causes bone fragility and deformity. Prominent extra-skeletal accessory manifestations of OI comprise blue/gray sclerae, hearing impairment, lung abnormalities and hypercalciuria. Cases of OI in cattle have been reported. However, no causative mutations have been identified in cattle so far. Aim To report a possible oligogenic origin identified in a calf from clinically healthy parents suffering from OI. Materials and Methods A neonatal embryo transfer male Holstein calf developing multiple fractures with bone tissue showing marked osteopenia was used for whole genome re-sequencing as well as its parents. In addition, 2,612 randomly chosen healthy Holstein cattle were genotyped as well as controls. Results Sixteen candidate genes with potential protein-altering variants were selected revealing non-synonymous variants only within IFITM5 and CRTAP genes. However, in-depth gene analysis did not result in the identification of a single causative mutation in the OI calf. Conclusion The analysis of the OI case revealed a possible oligogenic origin of the disease attributable to additive effects of three candidate genes, i.e., ABCA13, QRFPR, and IFTIM5. Clinical relevance Most OI cases in humans and domestic animals reported so far are caused by distinct dominant or recessive monogenic mutations, therefore a potential oligogenic additive genetic effect is a novel finding. Furthermore, the case presented here demonstrates that cross-species genetic analyses might not always be straightforward.

A novel mutation combining with rs66612022 in a Chinese pedigree suggests a new pathogenesis to osteogenesis imperfecta via whole genome sequencing.

Osteogenesis imperfecta (OI) is a rare heritable disease with systemic connective tissue disorder. Most of the patients represent autosomal dominant form of OI, and are usually resulting from the mutations in type I collagen genes. However, the gene mutations reported previously only account for ∼70% of the OI cases. Here, in a Chinese OI family, we examined seven patients and nine normal individuals using the whole genome sequencing and molecular genetic analysis. The mutation of rs66612022 (COL1A2:p.Gly328Ser) related to glycine substitution was found in the seven patients. Moreover, we identified a novel missense mutation (HMMR:p.Glu2Gln). Interestingly, the individuals of this family with both the mutations were suffering from OI, while the others carried one or none of them are normal. The mutations of COL1A2 and HMMR and their combined effect on OI would further expand the genetic spectrum of OI.

A novel nonsense variant in COL1A1 gene in a family with clinical symptoms of osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a genetic disorder characterized by fragile bones. Most OI cases are caused by defects in type I collagen structure or synthesis. Mutations in collagen specific molecular chaperone Hsp47, specifically L78P and L326P, lead to OI, yet these mutants are not fully characterized. Here, we found that both Hsp47 mutants were structurally unstable and formed high molecular weight complexes. They were degraded by the ubiquitin-proteasome system, and the collagen-binding ability of the mutants was significantly lower than that of the wild type. Although the chemical chaperone 4-PBA partially restores the solubility of the Hsp47 OI mutants, collagen-binding activity of Hsp47 was not improved.

Comprehensive genetic analyses using targeted next-generation sequencing and genotype-phenotype correlations in 53 Japanese patients with osteogenesis imperfecta

SummaryTo elucidate mutation spectrum and genotype-phenotype correlations in Japanese patients with OI, we conducted comprehensive genetic analyses using NGS, as this had not been analyzed comprehensively in this patient population. Most mutations were located on COL1A1 and COL1A2. Glycine substitutions in COL1A1 resulted in the severe phenotype.IntroductionMost cases of osteogenesis imperfecta (OI) are caused by mutations in COL1A1 or COL1A2, which encode α chains of type I collagen. However, mutations in at least 16 other genes also cause OI. The mutation spectrum in Japanese patients with OI has not been comprehensively analyzed, as it is difficult to identify using classical Sanger sequencing. In this study, we aimed to reveal the mutation spectrum and genotype-phenotype correlations in Japanese patients with OI using next-generation sequencing (NGS).MethodsWe designed a capture panel for sequencing 15 candidate OI genes and 19 candidate genes that are associated with bone fragility or Wnt signaling. Using NGS, we examined 53 Japanese patients with OI from unrelated families.ResultsPathogenic mutations were detected in 43 out of 53 individuals. All mutations were heterozygous. Among the 43 individuals, 40 variants were identified including 15 novel mutations. We found these mutations in COL1A1 (n = 30, 69.8%), COL1A2 (n = 12, 27.9%), and IFITM5 (n = 1, 2.3%). Patients with glycine substitution on COL1A1 had a higher frequency of fractures and were more severely short-statured. Although no significant genotype-phenotype correlation was observed for bone mineral density, the trabecular bone score was significantly lower in patients with glycine substitutions.ConclusionWe identified pathogenic mutations in 81% of our Japanese patients with OI. Most mutations were located on COL1A1 and COL1A2. This study revealed that glycine substitutions on COL1A1 resulted in the severe phenotype among Japanese patients with OI.

Results of stapedotomy in otosurgical treatment of adult patients with osteogenesis imperfecta

ObjectiveThis is a retrospective study of hearing results and characteristics of osteogenesis imperfecta (OI) patients treated for hearing loss by stapedotomy at tertiary reference center. MethodsThis study enrolled 20 patients with a clinical diagnosis of OI- (11M:9F). 18 patients (90%) underwent surgery due to hearing loss in the period 2003–16. The audiometric analysis provides the pure tone audiometry results of stapedotomy in adult patients in 2 periods (≤12 months and >12 months).Air-bone gap (ABG), hearing gain (HG), and changes in air and bone conduction thresholds after surgical treatment were analyzed. ResultsIn short-time follow-up we noted statistically significant improvement in mean AC thresholds and ABG (p < 0.001 for both), change in mean BC thresholds was statistically negligible. Comparing the observation periods short-term and long-term, it was found that AC thresholds, ABG, HG, ABG closure did not significantly change, although BC thresholds and BC closure deteriorated significantly (p < 0.05). ConclusionStapes surgery for OI can be considered as a method of treating the conductive and/or mixed hearing loss suffered by these patients; however, the surgery is more difficult than that for otosclerosis because OI cases often have extremely difficult anatomical conditions. The hearing results of OI stapes surgery differ from typical otosclerosis cases, with the ABG closure not being as good. In addition, sensorineural hearing loss inevitably progresses.

Compound heterozygous mutations in COL1A1 associated with an atypical form of type I osteogenesis imperfecta.

Heterozygous mutations in the genes encoding the proα1(I) or proα2(I) chains of type I procollagen (COL1A1 and COL1A2, respectively) account for most cases of osteogenesis imperfecta (OI), a disorder characterized by reduced bone strength and increased fracture risk. COL1A1 mutations can also cause rare cases of Ehlers-Danlos syndrome (EDS), a disorder that primarily affects connective tissue and often includes reduced bone mass. Here we present a kindred of three young siblings ages 1-4 years old whose mother has a history of mild type I OI. All three children are compound heterozygotes for COL1A1 mutations, with a novel frameshift mutation (c.2522delC; p.Pro841Leufs*266) from their mother and a known missense mutation (c.3196C>T; p.R1066C) from their clinically unaffected father, which has previously been described as causing a combined type I OI/EDS phenotype. The three children exhibit features of both COL1A1 mutations: early and frequent long bone fractures, joint hyperextensibility, and blue sclerae. We describe three siblings who are the first reported surviving subjects with biallelic pathogenic COL1A1 mutations. They have a more severe form of type I OI with features of EDS that represents their compound heterozygosity for two deleterious COL1A1 mutations. Their long-term outcomes are yet to be determined.

Molecular spectrum and differential diagnosis in patients referred with sporadic or autosomal recessive osteogenesis imperfecta.

BackgroundOsteogenesis imperfecta (OI) is a heterogeneous bone disorder characterized by recurrent fractures. Although most cases of OI have heterozygous mutations in COL1A1 or COL1A2 and show autosomal dominant inheritance, during the last years there has been an explosion in the number of genes responsible for both recessive and dominant forms of this condition. Herein, we have analyzed a cohort of patients with OI, all offspring of unaffected parents, to determine the spectrum of variants accounting for these cases. Twenty patients had nonrelated parents and were sporadic, and 21 were born to consanguineous relationships.MethodsMutation analysis was performed using a next‐generation sequencing gene panel, homozygosity mapping, and whole exome sequencing (WES).ResultsPatients offspring of nonconsanguineous parents were mostly identified with COL1A1 or COL1A2 heterozygous changes, although there were also a few cases with IFITM5 and WNT1 heterozygous mutations. Only one sporadic patient was a compound heterozygote for two recessive mutations. Patients offspring of consanguineous parents showed homozygous changes in a variety of genes including CRTAP,FKBP10,LEPRE1,PLOD2,PPIB,SERPINF1,TMEM38B, and WNT1. In addition, two patients born to consanguineous parents were found to have de novo COL1A1 heterozygous mutations demonstrating that causative variants in the collagen I structural genes cannot be overlooked in affected children from consanguineous couples. Further to this, WES analysis in probands lacking mutations in OI genes revealed deleterious variants in SCN9A,NTRK1, and SLC2A2, which are associated with congenital indifference to pain (CIP) and Fanconi–Bickel syndrome (FBS).ConclusionThis work provides useful information for clinical and genetic diagnosis of OI patients with no positive family history of this disease. Our data also indicate that CIP and FBS are conditions to be considered in the differential diagnosis of OI and suggest a positive role of SCN9A and NTRK1 in bone development.

Mutants of collagen-specific molecular chaperone Hsp47 causing osteogenesis imperfecta are structurally unstable with weak binding affinity to collagen

Osteogenesis imperfecta (OI) is a genetic disorder characterized by fragile bones. Most OI cases are caused by defects in type I collagen structure or synthesis. Mutations in collagen specific molecular chaperone Hsp47, specifically L78P and L326P, lead to OI, yet these mutants are not fully characterized. Here, we found that both Hsp47 mutants were structurally unstable and formed high molecular weight complexes. They were degraded by the ubiquitin-proteasome system, and the collagen-binding ability of the mutants was significantly lower than that of the wild type. Although the chemical chaperone 4-PBA partially restores the solubility of the Hsp47 OI mutants, collagen-binding activity of Hsp47 was not improved.

Osteogenesis imperfecta

Osteogenesis imperfecta (OI) describes a group of rare heritable disorders of connective tissue characterized by varying degrees of low bone mass and increased susceptibility to fractures. Most cases of OI are due to heritable defects in the synthesis or metabolism of type I collagen. The resulting bone tissue is prone to fracture due to a combination of alterations in both material and architectural qualities. The range of OI encompasses antenatal lethality to individuals with only small numbers of fractures. There are various classifications of OI, some of which have expanded along with understanding of the genetic diversity of rarer forms of OI. Accurate diagnosis at the earliest opportunity is important because specialist multidisciplinary input can dramatically improve outcomes in both the short and long term. Bisphosphonates are widely recognized as standard of care in childhood OI but the maximum benefits are only realized alongside the delivery of a multidisciplinary package of care including physiotherapy. There should be a planned and timely transfer of care to an appropriately skilled team based in adult services.

Spectrum of COL1A1/2 mutations and gene diagnosis in Chinese patients with osteogenesis imperfecta

To identify mutations of the type I collagen genes (COL1A1 and COL1A2) in the affected with osteogenesis imperfecta (OI), to establish the spectrum of COL1A1/2 mutations in Chinese OI patients, and to provide prenatal gene diagnosis to the fetuses at high risk. Genomic DNA was extracted from peripheral blood by the standard SDS-proteinase K-phenol/chloroform method. All the coding regions and exon/intron boundaries of COL1A1/2 were screened in 200 OI cases by conventional Sanger sequencing and targeted next-generation sequencing (NGS) on Ion Torrent-personalized genome sequencing operation (Ion PGM™). For familial cases, candidate mutations were validated in all available family members using high resolution melting analysis (HRM). In sporadic cases, only parents were examined to determine the origin of the identified mutation.Prenatal gene diagnosis was carried out by PCR direct sequencing and linkage analysis using microsatellite markers. In total, the authors identified 125 differently pathogenic mutations, including 74 in COL1A1 and 51 in COL1A2, in 158 probands, with a mutation detection rate of 79% (158/200). Among the 125 identified mutations, there were 63 novel mutations (33 in COL1A1 and 30 in COL1A2) and 13 recurrent mutations found in 46 probands (seven mutations recurring for two times, and the other six mutations recurring for more than 4 times). They performed prenatal genetic testing in 74 fetuses and found that 40 ones carried COL1A1/2 mutations identified in the corresponding probands. The authors have developed a combined approach for genetic testing of OI, extended the COL1A1/2 mutation spectrum in Chinese OI patients, and confirmed gene diagnosis in a relatively large cohort of OI probands and fetuses.

Severe osteogenesis imperfecta caused by double glycine substitutions near the amino‐terminal triple helical region in COL1A2

Most cases of osteogenesis imperfecta (OI) are caused by heterozygous mutations in COL1A1 or COL1A2, the genes encoding the two type I procollagen alpha chains, proα1 (I) and proα2 (I). We report on a unique case of severe OI, a long term survivor of lethal type II OI, rather than progressively deforming type III, due to double substitutions of glycine residues in COL1A2 (p.Gly208Glu and p.Gly235Asp), located on the same allele. To the best of our knowledge, this is the first example of a patient with double COL1A2 glycine substitution mutations on the same allele. We show for the first time that double COL1A2 glycine substitution mutations located near the amino-terminal triple helical region, which individually are likely to result in mild OI, cause severe OI in combination.

Osteogenesis imperfecta

Osteogenesis imperfecta (OI) is the most common genetic disease of bone and is characterized by fragile bones and growth disorders of varying severity. Most cases of OI are inherited autosomal dominant and caused by a mutation in the collagen type I gene. Indications for OI are bone fragility, stunted growth, scoliosis, skull deformities, blue sclera, loss of hearing, dentinogenesis imperfecta and increased laxity of ligaments and skin. In most cases it is possible to make a clinical diagnosis but a skin biopsy or genetic testing can be useful; however, negative results for these tests do not exclude OI. Therapy must be carried out in a multidisciplinary team and includes conservative (e.g. physiotherapy, rehabilitation programs and orthopedic aids), operative (e.g. intramedullary stabilization procedures) and pharmaceutical (e.g. biphosphonates and growth hormones) procedures. The prognosis depends on the type of OI and ranges from normal life expectations for type 1 patients up to up to perinatal mortality for type II patients.