Surgical treatment of osteogenesis imperfecta: a summary of the incidence of femoral implant-related complications in children with Sillence type I, III and IV.

PURPOSE: This study explored the incidence of IRCs used in the procedures of the femur in children with osteogenesis imperfecta (OI) and investigated the independent risk factors of IRCs. METHODS: Three hundred eight-eight cases of surgical data about children with OI were included, who were treated with plate, elastic nail, Kirschner wire and telescopic rod. The choice of different procedures depended on the age of children, the status of femur and the availability of devices. Patient demographics and major IRCs were recorded to compare the outcomes of the four procedures. Then, Cox proportional hazard regression was used to analyse the independent risk factors of IRC, and subgroup analysis was applied to further verify the above results. RESULTS: The total incidence of IRC in the four groups was 90.1% (191/212) for plate, 96.8% (30/31) for Kirschner wire, 87.7% (57/65) for elastic nail and 30.0% (24/80) for telescopic rod. The incidence of IRC in the telescopic rod was lower than that in plate, elastic nail and Kirschner wire (P < 0.001). Cox proportional hazard regression analysis confirmed that procedure was the independent risk factor of IRC (HR, 0.191; 95% CI, 0.126-0.288; P < 0.001), fracture (HR, 0.193; 95% CI, 0.109-0.344; P < 0.001) and deformity (HR, 0.086; 95% CI, 0.027-0.272; P < 0.001). In addition, age of surgery was the independent risk factor of fracture (HR, 0.916; 95% CI, 0.882-0.952; P < 0.001) and deformity (HR, 1.052; 95% CI, 1.008-1.098; P = 0.019). Subgroup analysis confirmed that age of surgery, gender, classification, preoperative state and angle did not affect the effect of telescopic rod on reducing the risk of IRCs. CONCLUSIONS: In our cohort, lower incidence of IRCs was observed in telescopic rod group compared with plate, Kirschner wire and elastic nail. Procedure and age of surgery were independent risk factors of fracture. Likewise, procedure and age of surgery were independent risk factors of deformity, and procedure was independent risk factors of IRC.

Which is the best femoral implant in children with osteogenesis imperfecta? a retrospective cohort study of 783 procedures.

BACKGROUND: Osteogenesis imperfecta (OI) is a hereditary genetic disorder characterized by bone fragility and extremity deformities. The surgical management for long-bone fractures and deformities in OI remains a challenge. We aimed to compare clinical outcomes after femoral surgery splinted with the telescopic rod, the plate and screws, the elastic nail and the non-elongating rod in setting of OI. METHODS:  A retrospective cohort study included 783 femoral procedures (mean age 6.00 (interquartile range (IQR) 5.00) years, 335 (42.8%) females) was conducted, and individuals were categorized into four groups according to implants. After verifying comparability among the groups, revision rate and implant survival period were compared among the Sillence types and the same comparison were made among four groups within each Sillence type. The incidence of refractures, deformities, and implant-related complications were also compared among the four groups. RESULTS: There were no significant differences in demographic information among the four groups in terms of sex (p = 0.101), laterality (p = 0.587), Sillence type (p = 0.122), and postoperative follow-up period (p = 0.214). In total, children with Sillence type III had the highest revision rate and the shortest implant survival period; children with Sillence type I had the lowest revision rate and the longest implant survival period; and children with Sillence type IV had the revision rate and the implant survival period between those observed in Sillence types I and III. In Sillence types III and IV, the telescopic rod had lower revision rate (III 24.8%; IV 20.9%) compared to the plate (III 97.2%, p<0.001; IV 80.3%, p<0.001), the elastic nail (III 100.0%, p=0.019; IV 73.9%, p<0.001) and the non-elongating rod (III 65.0%, p<0.001; IV46.9%, p<0.001); the median implant survival period of the telescopic rod (III 48.00 (IQR 28.50) months; IV 43.00 (33.00) months) is longer than the plate (III 11.00 (9.00) months, p<0.001; IV 19.00 (20.00) months, p<0.001), the elastic nail (III 45.00 (37.75) months, p=1.000; IV 19.00 (35.00) months, p=0.028) and the non-elongating rod (III 39.00 (31.75) months, p=0.473; IV 38.50 (29.75) months, p=1.000).A similar trend was observed in Sillence type I (p = 0.063, p = 0.003; respectively). In addition, the incidence of refracture (15.5%), deformity (2.8%) and implant-related complications (23.1%) were also statistically lower in the telescopic rod group. CONCLUSION: In our cohort, lower revision rate and longer implant survival period were observed in telescopic rod group. This was mainly due to the significant lower incidence of refracture, deformity and implant-related complications with the use of telescopic rod.

[Identification of pathogenic variants in three Chinese patients with McCune-Albright syndrome].

OBJECTIVE: To explore the genetic basis for three Chinese patients with McCune-Albright syndrome (MAS). METHODS: Three children who had respectively presented at Shandong Provincial Hospital in April 2019 and Peking Union Medical College Hospital in August 2020 and May 2021 were selected as the research subjects. Peripheral blood samples of the probands and their family members were taken for the extraction of genomic DNA. Potential variants were screened by whole exome sequencing (WES), and candidate variants were validated by Sanger sequencing of the patients and their family members. RESULTS: The proband from family 1 was found to harbor a heterozygous c.601C>T (p.R201C) missense variant in exon 8 of the GNAS gene, whilst the probands from families 2 and 3 were both found to harbor a heterozygous c.602G>A (p.R201H) missense variant in exon 8 of the GNAS gene. Both variants were known to be pathogenic, and all probands were found to be mosaics for the corresponding variants but with various degrees. CONSLUSION: WES can effectively diagnose MAS and other somatic genetic disorders. In this study, the combined WES and Sanger sequencing have verified the degree of mosaicisms of pathogenic variants in the three MAS patients, albeit no apparent correlation was found between the degree of mosaicisms and the phenotype of patients. Above finding has provided a basis for genetic counseling and prenatal diagnosis for the affected families.

Mutation spectrum of COL1A1/COL1A2 screening by high-resolution melting analysis of Chinese patients with osteogenesis imperfecta.

High-resolution melting (HRM) analysis has been shown to be a time-saving method for the screening of genetic variants. To increase the precision of the diagnosis of osteogenesis imperfecta (OI), we used HRM to explore COL1A1/COL1A2 mutations in 87 Chinese OI patients and to perform population-based studies of the relationships between their genotypes and phenotypes. Peripheral blood samples were collected from the 87 non-consanguineous probands. The coding regions and exon boundaries of COL1A1/COL1A2 were detected by HRM and confirmed by Sanger sequencing. The functional effects of mutations were predicted through bioinformatic tools. Mutations were detected in 70.3% of familial cases and 40% of sporadic cases (p < 0.01). Compared with COL1A1 mutations, patients with COL1A2 mutations were more prone to severe phenotypes. Helical mutations (caused by substitution of the glycine within the Gly-X-Y triplet domain) were more likely to occur in patients with type III and IV (p < 0.05). Haploinsufficiency mutations (caused by frameshift, nonsense, and splice-site mutations) appeared more frequently in patients with type I (p < 0.05). Compared with the Sanger sequencing and whole exome sequencing (WES), HRM was found to reduce total costs by 78%- 80% in patients who had a positive HRM separate melting curve. Our findings suggest that HRM would greatly benefit small and understaffed hospitals and laboratories, and would facilitate the accurate diagnosis and early treatment of OI in remote and less developed regions.

Genotypic and phenotypic characterization of Chinese patients with osteogenesis imperfecta.

Osteogenesis imperfecta (OI) is a rare hereditary skeletal dysplasia, characterized by recurrent fractures and bone deformity. This study presents a clinical characterization and mutation analysis of 668 patients, aiming to establish the mutation spectrum and to elucidate genotype-phenotype correlations in Chinese OI patients. We identified 274 sequence variants (230 in type I collagen encoding genes and 44 in noncollagen genes), including 102 novel variants, in 340 probands with a detection rate of 90%. Compared with 47 loss-of-function variants detected in COL1A1, neither nonsense nor frameshift variants were found in COL1A2 (p < 0.0001). The major cause of autosomal recessive OI was biallelic variants in WNT1 (56%, 20/36). It is noteworthy that three genomic rearrangements, including one gross deletion and one gross duplication in COL1A1 as well as one gross deletion in FKBP10, were detected in this study. Of ten individuals with glycine substitutions that lie towards the N-terminal end of the triple-helical region of the α1(I) chain, none exhibited hearing loss, suggesting a potential genotype-phenotype correlation. The findings in this study expanded the mutation spectrum and identified novel correlations between genotype and phenotype in Chinese OI patients.

Novel NTRK1 mutations in Chinese patients with congenital insensitivity to pain with anhidrosis.

Congenital insensitivity to pain with anhidrosis (CIPA) is a rare autosomal recessive disorder, characterized by loss of algesthesis and inability to sweat. CIPA is known to be caused by mutations in the neurotrophic tyrosine kinase receptor type 1 gene ( NTRK1). However, the details of NTRK1 mutations in Chinese CIPA patients remain unclear. In the present study, we recruited 36 CIPA patients from 34 unrelated families in mainland China. Blood samples from these patients and their available familial members were collected and subjected to genetic analysis. We identified 27 mutations in NTRK1 from this cohort, including 15 novel mutations. Interestingly, we discovered two forms of novel recurrent mutations: the first was a large intragenic deletion c.429-374_717 + 485del mediated by recombination between Alu elements, and the second was a deep intronic substitutions c.[851-798C > T;851-794C > G]. All probands were homozygotes or compound heterozygotes of these mutations. Current findings expand our knowledge about the mutation spectrum of NTRK1 in Chinese CIPA patients and provide more evidence for precise diagnosis of the clinically suspected patients with CIPA.

[Genetic mutation and clinical features of osteogenesis imperfecta type V].

OBJECTIVE: To explore genetic mutations and clinical features of osteogenesis imperfecta type V. METHODS: Clinical record of five patients (including one familial case) with osteogenesis imperfecta type V were retrospectively analyzed. Peripheral blood samples of the patients, one family member, as well as healthy controls were collected. Mutation of IFITM5 gene was identified by PCR amplification and Sanger sequencing. RESULTS: A heterozygous mutation (c.-14C>T) in the 5-UTR of the IFITM5 gene was identified in all of the patients and one mother. The clinical findings included frequent fractures and spine and/or extremities deformities, absence of dentinogenesis imperfecta, absence of hearing impairment, and blue sclera in 1 case. Radiographic findings revealed calcification of the interosseous membrane between the radius-ulna in all cases. Hyperplastic callus formation was found in 3 cases. Four had radial-head dislocation. CONCLUSION: A single heterozygous mutation c.-14C>T was found in the 5-UTR of the IFITM5 gene in 5 patients with osteogensis imperfecta type V. The patients showed specific radiological features including calcification of interosseous membrane, hyperplastic callus formation, and radial-head dislocation.

[Analysis of gross deletions of COL1A1/2 genes in Chinese families affected with osteogenesis imperfecta].

OBJECTIVE: To identify deletion of large fragment in COL1A1/2 genes among patients with osteogenesis imperfecta (OI). METHODS: Genomic DNA was extracted from peripheral blood samples by a standard SDS-proteinase K-phenol/chloroform method. Multiplex ligation-dependent probe amplification (MLPA) was performed to detect gross deletions of the COL1A1/2 genes among 46 patients affected with OI, in whom no mutation was detected in the sequences of the COL1A1/2 genes. RESULTS: Heterozygous deletions of the entire COL1A1 gene and exon 20 of the COL1A2 gene were detected in probands A and B, respectively, and no gross deletion was found in the remaining 44 samples. The MLPA result of proband A was confirmed by fluorescence quantitative PCR (Q-PCR) in his family. A further conjunction point analysis through gap-PCR and DNA sequencing revealed deletion of exons 17 to 23 in the COL1A2 gene, and a 637 bp-insertion from chromosome 5 in the proband B. CONCLUSION: Two gross deletions have been found in the genes coding for collagen type I in the Chinese OI population, and the deletion of exons 17 to 23 in the COL1A2 gene is a novel mutation. This work not only has expanded the mutation spectrum of the COL1A1/2 gene, but also provided a support for prenatal genetic diagnosis for the families.

[Analysis of type IV osteogenesis imperfecta caused by two mutations occurred simultaneously in COL1A1 gene in a Chinese child].

OBJECTIVE: To detect potential mutations of COL1A1 and COL1A2 genes with polymerase chain reaction-high-resolution melting analysis(PCR-HRMA) in a proband diagnosed with osteogenesis imperfecta (OI). METHODS: Peripheral blood samples were collected from the proband and members of his family as well as healthy controls. The mutations were detected by PCR-HRMA and confirmed by direct sequencing. Potential effects of the mutations were predicted using softwares including PolyPhen, SIFT and Align GVGD. RESULTS: The PCR-HRMA has indicated mutations in exon 45 of the COL1A1 gene in the proband as well as his parents, which were presented as the difference in the melting curves between the patients and the control samples. Sequencing analysis confirmed that the proband has carried two heterozygous mutations (c.3235G>A, p.Gly1079Ser and c.3247G>A, p.Ala1083Thr) in exon 45 of the COL1A1 gene. Among them, c.3235G>A was predicted to have impeded alpha helix structure domain, which was inherited from the father who also had OI. c.3247G>A was inherited from mother who had a normal phenotype. All three softwares predicted that the c.3235G>A mutation can interfere with the function of the protein, while the c.3247G>A may have a benign effect by PolyPhen analysis. CONCLUSION: The study identified two mutations (c.3235G>A and c.3247G>A) occurred simultaneously in COL1A1 gene in a case. The case is the first reported in human collagen mutation database. As identified,mutation of c.3235G>A may be the major cause of the disease in the proband.

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

OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Mutational and structural characteristics of four novel heterozygous C-propeptide mutations in the proα1(I) collagen gene in Chinese osteogenesis imperfecta patients.

OBJECTIVE: Osteogenesis imperfecta (OI) with C-propeptide mutations in proα1(I) collagen gene are rarely reported. We report four novel C-propeptide mutations in COL1A1 gene from Chinese OI patients. METHODS: Clinical characteristics and radiographic findings were described for four OI patients with C-propeptide mutations in proα1(I) collagen gene. Mutations were identified by traditional DNA sequencing based on PCR. The locations of mutations were mapped, and in silico prediction was conducted to analyse their effects on protein structure. Histology studies of skin, bone and muscle tissues were performed. RESULTS: All four C-propeptide heterozygous mutations identified were in the COL1A1 gene. Heterozygous mutation of c.4021C>T (p.Q1341X) disrupted the chain recognition sequences and was found in patients with type IV OI. Mutations of c.3893C>A (p.T1298N) and c.3897C>A (p.C1299X) impeded the formation of disulphide bonds and were associated with type IV OI phenotype. Missense mutation of c.3835A>C (p.N1279H) disrupted Ca(2+) binding and led to a severe type III OI phenotype. In silico programs predicted damaging effects for the patients with type III OI and the creation of an exonic splicing enhancer hexamer sequence for the type IV patients. Expansion of the bone marrow cavity and disorganization of osteocyte alignment was evident in bone specimens; and muscle atrophy and enlargement of intramuscular connective tissue were found in muscle specimens. CONCLUSIONS: Four novel C-propeptide mutations in proα1(I) collagen gene were identified in Chinese OI patients, and their clinical severity ranged from moderate type IV to severe type III. In silico prediction of the mutation effect and histological characteristics of tissue specimens was in accordance with the OI phenotypes.

[Screening and analysis of a new mutation of COL1A1 gene in a family with osteogenesis imperfecta].

OBJECTIVE: To investigate mutation of COL1A1 gene and analyze the relationship between genotype and clinical phenotype in a family with osteogenesis imperfecta (OI). METHODS: The family history of an OI pedigree, along with clinical data, was collected. Blood samples from the proband and his families, as well as 50 normal controls, were collected. Mutation of COL1A1 gene was screened using PCR-high resolution melting (PCR-HRM) and validated by sequencing. RESULTS: PCR HRM method showed an abnormal result in proband COL1A133_34 exons, which Tm was 87.7℃, in contrast to the normal control (wt) Tm of 87.9±0.06℃. There was a significant difference between the proband and the normal control with the standardization curve and the difference curves. DNA sequencing showed that Y9COL1A1 gene exons 33_34 has lost a C base (c.2321delC), which resulted in a frameshift mutation and caused an premature termination codon (UAA) at amino acid 334, i.e., p.Pro774LeufsX334 The father and grandfather of the proband, both suffered from OI, were verified to be heterozygous for the same mutation. The same mutation was not found in 50 normal controls. Database search confirmed this to be a novel mutation. Pedigree analysis suggested that it has an autosomal dominant inheritance. The proband and patients from the family were clinically diagnosed as OI type I. CONCLUSION: The study has identified a novel mutation of COL1A1 gene, c.2321delC. This frameshift mutation has caused a premature stop codon and reduced collagen type synthesis, characterized by a lighter OI clinical phenotype.

Genetic etiology study in a large cohort with congenital insensitivity to pain with anhidrosis.

ABSTRACT: Pathogenic variations in the NTRK1 can cause congenital insensitivity to pain with anhidrosis (CIPA), a rare autosomal recessive inherited neuropathy. The precise diagnosis of CIPA relies on the identification of pathogenic genotypes. Therefore, it is essential to expand the NTRK1 variation spectrum and improve molecular diagnosis methods. In this study, 74 probands with typical manifestations of CIPA but unknown genotypes were recruited. A comprehensive molecular genetic analysis was performed to identify variations in the NTRK1, using techniques including Sanger and next-generation sequencing, bioinformatic analysis, quantitative polymerase chain reaction (qPCR), gap-PCR, short tandem repeat (STR) genotyping, and reverse-transcription PCR. In addition, functional assays were conducted to determine the pathogenicity of variants of uncertain significance (VUS) and further characterized changes in glycosylation and phosphorylation of 14 overexpressed mutant vectors with variants at different domains in the TrkA protein, which is encoded by NTRK1. A total of 48 variations in the NTRK1 were identified, including 22 novel ones. When combined with data from another 53 CIPA patients examined in our previous work, this study establishes the largest genotypic and phenotypic spectra of CIPA worldwide, including 127 CIPA families. Moreover, functional studies indicated that the pathogenicity of VUS mainly affected insufficient glycosylation in the extracellular domain and abnormal phosphorylation in the intracellular domain. This study not only provides important evidence for precise diagnosis of CIPA but also further enriches our understanding of the pathogenesis of this disease.

The patient-related factors in revision procedures on tibia of patients with osteogenesis imperfecta treated with the Peter-Williams nail.

OBJECTIVE: To investigate the patient-related factors that affect the revision rate for the tibia in patients with osteogenesis imperfecta treated with the Peter-Williams nail, and to explore the relationship between the risk factors and complications postsurgery. METHODS: We retrospectively analysed the data of 211 patients (93 females (44.08%) and 118 males (55.92%)) with osteogenesis imperfecta treated with Peter-Williams. The factors affecting surgical revision were analysed by performing binary logistic regression. Then, a total of 211 patients with type III, type I or type IV OI were divided into five groups according to the results of regression. Statistical comparison of these groups was performed to further investigate the relationship between patient-related factors and revision procedures. Statistical comparison was also performed to analyse the relationship between the classification and postoperative complications. RESULTS: Among the 211 patients who underwent surgery, 40 had type I OI, 109 had type IV OI, and 62 had type III OI. Binary logistic regression revealed that the classification (OR = 3.32, 95% CI 1.06-10.39, P = 0.039) and initial operation age (OR = 0.83, 95% CI 0.76-0.92, P < 0.001) were significantly correlated with revision procedures. In type III patients, the initial operation age was significantly correlated with revision procedures (P < 0.001), and the revision rate was lower in patients aged 9 to12 years (P = 0.001). In type I and IV patients, the initial operation age was not significantly correlated with revision procedures (P = 0.281). Classification had a significant effect on postoperative deformity (P = 0.003). CONCLUSIONS: The study reported that the age of initial surgery and classification were the influencing factors affecting the revision procedures of tibia in patients with osteogenesis imperfecta treated with the Peter-Williams nail. In patients with type III disease, the revision rate was lower individuals aged 9-12 years old, and a higher incidence of postoperative deformity was observed.

CRISPR/Cas9 correction of a dominant cis-double-variant in COL1A1 isolated from a patient with osteogenesis imperfecta increases the osteogenic capacity of induced pluripotent stem cells.

Osteogenesis imperfecta (OI) is a hereditary skeletal disorder that is mainly caused by variants in COL1A1/2. So far, no specific treatment has been developed to correct its underlying etiology. We aimed to gain a better understanding of the pathological mechanisms of OI and develop gene therapies to correct OI-causing variants. A de novel cis-double-variant c.[175C>T; 187T>A] in COL1A1 was identified from a 5-year-old OI patient by whole-exome sequencing (WES). Three peptide nucleic acids (PNAs) were designed and then transfected patient-derived fibroblasts. PNA2 affected the translational strand and induced an optimal interfering effect at 0.25µM concentration, proved by Sanger sequencing, qPCR, Western blot, and immunostaining. Additionally, induced pluripotent stem cells (iPSCs) were cultured from patient-derived fibroblasts. Clones of iPSCs with c.187T>A variant and those with both variants largely restored their osteogenic capacities after CRISPR/Cas9 gene editing, which corrected the variants. Importantly, correcting c.187T>A variant alone in CRISPR-edited iPSCs was sufficient to alleviate OI phenotypes, as indicated by increased levels of COL1A1, COL1A2, ALP mRNAs, and COL1A1 protein. Our findings suggest that c.187T>A is the dominant variant of cis-double-variant in COL1A1 that led to OI, and PNA interference and CRISPR/Cas9 gene editing may be new therapeutic tools for OI treatment. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Incidence and prevalence of 121 rare diseases in China: Current status and challenges: 2022 revision.

The current study updated data on the incidence and prevalence of 121 rare diseases listed in China's First List of Rare Diseases to provide rationales and references for the development and promotion of rare-disease-related policies. The National Health Commission of the People's Republic of China issued the Rare Disease Diagnosis and Treatment Guide (2019) (denoted here as China's Rare Disease Diagnosis and Treatment Guide). Then 121 diseases were registered with the national rare disease diagnosis and treatment network. The incidence/prevalence of 121 rare diseases varied from country to country. Data are available for a total of 76 rare diseases (76 of 121 rare diseases, 62.81%) in China, including data on the incidence of 23 rare diseases (19.01%) and data on the prevalence of 66 (54.55%). There are data on the incidence/prevalence of 112 rare diseases (112 of 121 rare diseases, 92.56%) at the global level, including data on the incidence of 86 rare diseases (71.07%) and data on the prevalence of 91 (75.21%). On average, the incidence of progressive muscular dystrophies, hyperphenylalaninemia, citrullinemia, and methylmalonic acidemia is over 1/10,000 in China. The prevalence of coronary artery ectasia, congenital scoliosis, retinitis pigmentosa, severe congenital neutropenia, congenital hyperinsulinemic hypoglycemia, and osteogenesis imperfecta is over 1/10,000 in China. All of these figures are beyond the cut-off of 1/10,000 according to the 2021 definition of rare diseases in China. As registration and investigation of rare diseases continues, the spectrum of rare diseases in some provinces is expanding. Diseases such as idiopathic pulmonary arterial hypertension, hepatolenticular degeneration, hemophilia, amyotrophic lateral sclerosis, idiopathic pulmonary fibrosis, and multiple sclerosis are relatively prevalent in some regions and cities of China. Registration efforts promote the correction of incidence/prevalence data, development of orphan drugs, coverage by medical insurance, and development of clinical and diagnostic pathways.

Identification of six novel variants from nine Chinese families with hypophosphatemic rickets.

BACKGROUND: Hypophosphatemic rickets (HR) is a rare genetic disorder associated with renal phosphate wasting and characterized by bone defects. Inactivating mutations in the phosphate regulating endopeptidase homolog X­linked gene (PHEX) account for most cases of HR. The aim of this study was to identify causative variants in nine unrelated Chinese families associated with HR, and to determine potential pathogenicity of the identified variants. METHODS: Genomic DNA was isolated from the peripheral blood of HR patients and their healthy relatives, followed by next-generation sequencing and/or Sanger sequencing. In silico prediction combined with conservation analysis was performed to assess the effects of the variants, and 3D protein modeling was conducted to predict the functional effects on the encoded protein. RESULTS: All HR patients recruited in this study displayed bone deformities and tooth agenesis, as well as reduced serum phosphate levels and elevated urine phosphate levels. Nine PHEX variants were identified in eight families, including four novel variants (c.1661_1726del, c.980A > G, c.1078A > T, and c.1017_1051dup). Of the nine identified PHEX variants, five caused a truncated protein, two caused an altered amino acid, and the other two were the canonical splicing variants. Novel variants c.1336G > A and c.1364 T > C in SLC34A3 were also found in one family. Conservation analysis showed that all the amino acids corresponding to the missense variants were highly conserved. In silico analysis and 3D protein structure modeling confirmed the pathogenicity of these variants. CONCLUSIONS: This study identified four novel variants in PHEX and two novel variants in SLC34A3 in a Chinese cohort with HR. Our findings highlight the dominant role of PHEX in HR, and expand the genotypic and phenotypic spectra of this disorder.

Current diagnosis and management of rare pediatric diseases in China.

This review categorizes and summarizes the rare pediatric diseases that have been included in the First List of Rare Diseases that was jointly published by the National Health Commission and four other government departments in China in 2018. In total, 58 diseases that develop during childhood are included. These diseases involve nine organ systems, including the musculoskeletal, respiratory, immune, endocrine and metabolic, nervous, cardiovascular, hematological, urinary, and integumentary systems. Affected children often have multiorgan involvement with various presentations. Severe diseases can cause acute symptoms starting in the neonatal period that lead to increased morbidity and mortality without prompt management. Early diagnosis and treatment can significantly change the course of a disease and improve its prognosis. This work systemically reviews the status of rare pediatric diseases with a relatively high incidence in the First List of Rare Diseases.

Comprehensive bioinformatic analysis of Wnt1 and Wnt1-associated diseases.

Wnt1 is the first member of the Wnt family that was identified. It is phylogenetically conserved and essential for oncogenesis and multiple developmental processes. This study has summarized diseases and mutations related to Wnt1. Wnt1 is involved in various cancers, genetic type XV osteogenesis imperfecta, osteoporosis, and neurological diseases. The expression of Wnt1 in normal tissues and different types of cancers and the potential survival of cancer were analyzed using experiment-based bioinformatic analysis. Systematic analysis indicated that abnormal expression of Wnt1 is significantly associated with cancers, such as kidney renal carcinoma, hepatocellular carcinoma, thyroid carcinoma, head and neck squamous cell carcinoma, and uterine corpus endometrial carcinoma. GeneMANIA and STRING predicted that 32 proteins were involved with Wnt1 in Wnt signaling pathways and sorting and secretion of Wnts. These interacting molecules significantly co-occurred according to cBioPortal analysis. Thirty-three genes with an alteration frequency of more than 50% were observed in several cancers like esophageal squamous cell carcinoma, melanoma, and non-small cell lung cancer. Functional and experiment-based bioinformatics indicated that Wnt1 may act as a target of a potential biomarker for various types of human cancers. Wnt1 and other Wnt1-related proteins and signaling pathways may be ways to treat osteoporosis.

Genotypic and Phenotypic Analysis in Chinese Cohort With Autosomal Recessive Osteogenesis Imperfecta.

Osteogenesis imperfecta (OI) is a rare heritable skeletal disorder which is mainly caused by defected type I collagen. Autosomal recessive OI (AR-OI) is caused by mutations of genes that are responsible for type I collagen modification and folding, and is often associated with more severe phenotypes. Due to the limited number of recessive OI patients, it has been difficult to study the mutation spectrum as well as the correlation of genotype and phenotype. This study recruited a Chinese cohort of 74 AR-OI families, aiming to establish the mutation spectrum and to examine the genotypic and phenotypic correlation. We identified 82 variants including 25 novel variants and 57 HGMD reported variants in these AR-OI patients, using whole exome sequencing/panel sequencing combined with Sanger sequencing. Pathogenic mutations were found at WNT1 (n = 30, 40.54%), SERPINF1 (n = 22, 29.73%), FKBP10 (n = 10, 13.51%), CRTAP (n = 3, 4.05%), P3H1 (n = 3, 4.05%), SERPINH1 (n = 2, 2.70%), SEC24D (n = 3, 4.05%), and PLOD2 (n = 1, 1.35%) respectively. Thus, WNT1 represents the most frequent pathogenic gene of AR-OI in Chinese population. The most common clinical manifestations of AR-OI patients include walking problem (72.86%), scoliosis (65.28%) and frequent fractures (fractures ≥2/year) (54.05%). Interestingly, ptosis represents a unique phenotype of patients carrying WNT1 variants, and it was rare in patients harboring other pathogenic genes. Our study expanded the mutation spectrum of AR-OI and enriched the knowledge of genotypic and phenotypic correlation in Chinese cohort with AR-OI.