Biallelic variants in SLC26A2 cause multiple epiphyseal dysplasia-4 by disturbing chondrocyte homeostasis.

BACKGROUND: Multiple epiphyseal dysplasia-4 (MED-4, MIM 226900) is a rare autosomal recessive disease characterized by disproportionate height and early onset osteoarthritis of the lower limbs. MED-4 is caused by homozygous or compound heterozygous pathogenic variants in the SLC26A2 gene. However, the underlying pathogenic mechanisms in chondrocytes remains unknown. This study aimed to identify the pathogenic variants within a MED-4 family and explore the molecular etiology of this condition in human primary chondrocyte cells. METHODS: Clinical data were recorded and peripheral blood samples were collected for analysis. Whole exome sequencing (WES) and bioinformatic analyses were performed to determine causative variants. Wild-type SLC26A2 and corresponding mutant expression plasmids were constructed and transfected into human primary chondrocytes. The expression and subcellular distribution of SLC26A2 protein in chondrocytes were detected by immunoblotting and immunofluorescence. Effects of these variants on chondrocytes viability and apoptosis were measured by Cell Counting Kit-8 (CCK-8) assay. Expression of genes related to cartilage homeostasis was subsequently analyzed by quantitative real-time polymerase chain reaction (qRT-PCR). RESULTS: We identified two compound heterozygous variants c.1020_1022delTGT(p.Val341del) and c.1262 T > C(p.Ile421Thr) in the SLC26A2 gene in the patients. Mutant SLC26A2Val341del and SLC26A2Ile421Thr proteins were distributed in relatively few cells and were observed only within the nucleus. The viability of chondrocytes with the SLC26A2 variant group was similar to the wild-type (WT) group. However, the protein expressions of SLC26A2Val341del and SLC26A2Ile421Thr were decreased compared with SLC26A2WT. Expression levels of matrix metallopeptidase 13 (MMP13), α-1 chain of type X collagen (COL10A1), and Runt-related transcription factor 2 (RUNX2) were significantly decreased in the variant group. However, aggrecan (ACAN) expression was higher in the variant group than the WT group. CONCLUSIONS: Overall, our data demonstrate that the variants p.Val341del and p.Ile421Thr in SLC26A2 cause MED-4 and that these two variants promote chondrocyte proliferation while inhibiting chondrocyte differentiation.

Multiple Epiphyseal Dysplasia With Knee Joint Locking Symptoms Caused by Intra-articular Loose Bodies.

Multiple epiphyseal dysplasia (MED) is a congenital disease causing epiphyseal dysplasia in long bones. Herein, we report a case of a middle-aged man with bilateral knee joint locking symptoms who was diagnosed with multiple epiphyseal dysplasia caused by Matrilin-3 (MATN3) pathogenic variants and was successfully treated with arthroscopic loose body removal. A 48-year-old man has had bilateral knee pain since his twenties and underwent loose body removal of both knees in his thirties. He visited our hospital for worsening locking symptoms in both knees. Twenty years ago, his son had been diagnosed with suspected multiple epiphyseal dysplasia. Genetic and imaging testing confirmed his diagnosis of multiple epiphyseal dysplasia due to Matrilin-3 pathogenic variants. Arthroscopic loose body removal was performed, and the locking symptoms disappeared after surgery. Arthroscopic loose body removal was effective for the locking symptoms in a mild adult case of multiple epiphyseal dysplasias caused by Matrilin-3 pathogenic variants.

Further characterization of ARSK-related mucopolysaccharidosis type 10.

Mucopolysaccharidosis type 10 is caused by biallelic variants in ARSK, which encodes for a lysosomal sulfatase. To date, seven patients with a mild phenotype resembling spondyloepiphyseal dysplasia or multiple epiphyseal dysplasia have been described. In this report, we present two novel ARSK variants and report clinical and radiological findings of three patients. The patients' initial complaints were hip or knee pain and a waddling gait. All patients showed normal intelligence, normal hearing and eye examinations, and none had organomegaly. While typical dysostosis multiplex findings were not observed, mild platyspondyly with anterior beaking of some vertebral bodies, irregular vertebral endplates, wide ribs, inferior tapering of the ilea with a poorly developed acetabulum, irregularity of the central part of the femoral head, delayed ossification of the carpals were noted. Remarkably, all patients showed metaphyseal striation of the long bones, a crucial diagnostic clue to identify ARSK-related MPS type 10. Interestingly, vertebral involvement regressed during follow-up. On the other hand, hip dysplasia progressed in all patients. In conclusion, this study provides valuable long-term results on a recently discovered form of MPS.

The favorable outcome of Bernese periacetabular osteotomy for the hip osteoarthritis in multiple epiphyseal dysplasia.

BACKGROUND: Multiple epiphyseal dysplasia (MED) is a rare congenital bone dysplasia. Patients with MED develop secondary hip osteoarthritis as early as the third to the fourth decade. Currently, there is no consensus on the prevention of the progressive hip osteoarthritis secondary to MED. The Bernese periacetabular osteotomy (PAO) is a joint-preserving surgery to reshape acetabulum and extend femoral head coverage. However, there is no documentary evidence for the effect of the procedure on MED hips. PATIENTS AND METHODS: We analyzed the preliminary outcomes following the Bernese PAO in 6 MED hips. The average age at the time of surgery was 14.3 years (range from 11.4 to 17.2 years). For our study interest of time efficiency, radiographic parameters were analyzed preoperatively and 1 year postoperatively. The hip function was evaluated by the Harris Hip Score (HHS) before and after surgery. RESULTS: The mean follow-up time was 1.7 years. The mean lateral center-edge angle increased from 3.8° to 47.1° (p = 0.02), anterior center-edge angle increased from 7.3° to 35.1° (p = 0.02), and acetabulum index decreased from 27.8° to 14.6° (p = 0.04). The femoral head coverage ratio increased from 66.8% to 100% (p = 0.02). The post-operative anteroposterior pelvic radiograph demonstrated all preoperative broken Shenton lines were reversed. The mean HHS improved from 67.3 to 86.7 (p = 0.05). CONCLUSION: Bernese PAO is a feasible treatment for hip disorders in MED patients. It reshapes acetabular and femoral morphology efficiently. In our study, the preliminary results showed the procedure not only improved radiographic outcomes but also hip function.

Onychodystrophy with Multiple Epiphyseal Dysplasia: Literature Review.

Introduction: Onychodystrophy has been described in association with certain bone disorders, including Nail-Patella Syndrome, Hutchinson-Gilford Progeria Syndrome, Coffin-Siris Syndrome, and congenital brachydactyly. However, nail changes associated with multiple epiphyseal dysplasia (MED) has not been documented. Case Presentation: An 11-year-old male with history of MED presented with thickened, dystrophic appearing fingernails. Physical examination was significant for fingernail longitudinal ridges and grooves, thinning, and distal splitting. Dermoscopy revealed superficial desquamation. Nail clippings were negative for microbial pathogens. Hand X-rays showed brachydactyly, shortening of the metacarpals, and sclerotic epiphyses of the bilateral 5th distal phalanges and right 2nd distal phalanx. Conclusion: This is the first documented case of MED with onychodystrophy, supporting the link between phalangeal formation and nail development. It is important to perform a careful examination of the nail units in patients with skeletal dysplasia and screen patients with characteristic and unexplained nail changes for bony changes. Living with skeletal disease is extremely challenging, and treatment of associated nail disease can improve quality of life for these patients.

Multiple epiphyseal dysplasia tip 5: Case report a rare skeletal dysplasia presenting with repetitive joint pain in children.

INTRODUCTION AND IMPORTANCE: Multiple epiphyseal dysplasia, which affects the epiphysis of long bones, can show autosomal dominant and autosomal recessive inheritance patterns (Ballhausen et al., 2003 [1]). The symptoms typically appear in childhood, although they sometimes do not show symptoms until adulthood. The goals of treatment in children are to prevent the early onset of osteoarthritis, improve function, and educate patients and their families about the natural history and genetic basis of the disease. Some patients present to the clinic with only non-healing and unidentified joint pain. Although multiple epiphyseal dysplasia type 5 is a rare disease with autosomal dominant inheritance in general, it can also be observed with de novo mutation, although very rarely, without a family history. CASE PRESENTATION: 7-years-old male patient was admitted to our orthopedics outpatient clinic with complaints of joint pain, fatigue, and pain in the knees and ankles that had lasted for about 3 years. He had epicanthus, left hemifacial microsomia, and metacarpophalangeal joint laxity. The arm was proportional to the body. In the laboratory, there was no obvious finding other than vitamin D deficiency. The epiphyses, especially in the ankle, were dysplasic on Xray. After genetic tests we detected multiple epiphyseal dysplasia type 5, with de novo mutation, without family histories. CLINICAL DISCUSSION: Multiple epiphyseal dysplasia type 5, which is usually an autosomal dominant disease (Ballhausen et al., 2003 [1]) characterized by normal height; it is seen due to heterozygous mutation of matrilin-3 gene (MATN3) at 2p24.1 location. Early-onset osteoarthritis, multiple epiphyseal dysplasia, arthralgia, small proximal femoral epiphyses, wide and short femoral neck, coxa vara, high greater trochanter, small, irregular epiphyses (distal femoral, proximal tibia, distal radius, distal ulna), mild metaphyseal irregularities (distal femoral, proximal tibia, proximal humeri, distal radius, distal ulna), genu valgum may accompany. In hands; small, irregular epiphyses (first metacarpal), delayed carpal ossification may be seen. Delayed tarsal ossification can be observed in the feet. On the other hand, some patients present to the clinic with only non-healing and unidentified joint pain. Although multiple epiphyseal dysplasia type 5 a rare disease with autosomal dominant inheritance in general, it can also be observed like our case with de novo mutation, although very rarely, without a family history. CONCLUSION: Multiple epiphyseal dysplasia type 5 is a rare disease. It should be kept in mind that skeletal dysplasia should also be evaluated, although it is rarely seen in patients with persistent joint pain. Thus, we can both slow down the progression with early diagnosis of the patient and minimize the early surgical requirements.

Clinical and Genetic Characteristics of Multiple Epiphyseal Dysplasia Type 4.

Multiple epiphyseal dysplasias (MED) are a clinically and genetically heterogeneous group of skeletal dysplasias with a predominant lesion in the epiphyses of tubular bones. Variants in the SLC26A2 gene cause their autosomal recessive form (rMED or MED type 4). The accumulation of data regarding the genotype−phenotype correlation can help in the diagnosis and proper management of these patients. The aim of this study was to survey the clinical and genetic characteristics of 55 patients with MED type 4 caused by variants in the SLC26A2 gene. Diagnosis confirmation was carried out by radiography and custom panel sequencing consisting of 166 genes responsible for the development of hereditary skeletal pathology. This was followed by the validation of the identified variants using automated Sanger sequencing (for six patients) and the direct automatic Sanger sequencing of the coding sequence and the adjacent intron regions of the SLC26A2 gene for 49 patients. Based on the clinical and genetic analysis of our sample of patients, two main MED type 4 phenotypes with early and late clinical manifestations were identified. An early and more severe form of the disease was observed in patients with the c.835C > T variant (p.Arg279Trp), and the late and milder form of the disease was observed in patients with the c.1957T > A variant (p.Cys653Ser) in the homozygous or compound heterozygous state with c.26 + 2T > C. It was also shown that only three pathogenic variants were found in 95.3% of the alleles of Russian patients with MED type 4: c.1957T > A (p.Cys653Ser), c.835C > T (p.Arg279Trp), and c.26 + 2T > C; thus, it can be assumed that the primary analysis of these variants will contribute to the optimal molecular genetic diagnostics of MED type 4.

Exome sequencing revealed USP9X and COL2A1 mutations in a large family with multiple epiphyseal dysplasia.

Diagnosis of rare skeletal diseases is based primarily on clinical phenotype and radiographic analysis. Genetic etiology of these heterogeneous diseases remains largely unknown. Here, we report the identification of two genomic mutations using exome sequencing from patients with multiple epiphyseal dysplasia (MED) of an unusual family in autosomal dominant and X-linked inheritance. A dominant mutation (c.2224G > A; p.Gly687Ser) in the known causal COL2A1 gene was identified in three patients with MED, deformed femoral heads and vertebral dysplasia. Furthermore, a hemizygous mutation (c.2830G > A; p.Ala944Thr) in the USP9X gene was identified in the fourth patient with short stature, MED, deformed femoral head, thoracic and lumbar platyspondyly, right ankle condyle dysplasia, and subchondral sclerosis. This is the first identification of an X-linked candidate causative gene in a patient with MED, suggesting a new clinical entity. Our findings shed a new light on the role of USP9X in MED-associated disorders.

Double-layered patella management in total knee arthroplasty for secondary osteoarthritis: A case report.

Double-layered patella (DLP) is an osseous disorder associated with multiple epiphyseal dysplasia (MED). A thorough investigation should be conducted prior to surgery to assess the role of each layer and their vascularization in order to establish the best surgical strategy. We present the case of a woman in her late 50s with MED, bilateral DLP, and secondary osteoarthritis treated by a left total knee arthroplasty (TKA). To plan the surgical procedure, bilateral knee magnetic resonance imaging was obtained to study the anatomy of the two bony layers and their relationship to the extensor mechanism. In addition, a computed tomography angiography was performed to study the origins of arterial blood supply to the patella layers to avoid postoperative bone necrosis. During a standard TKA procedure, after adjusting the thickness of the posterior layer, we fused both layers using outside-in headless compressive screws. Clinical outcome was satisfactory with no anterior knee pain and radiographs showed signs of bone fusion between layers at last follow-up. No case report was found in the literature in which a full preoperative investigation was made to establish the best surgical management of a DLP during TKA. In such a case, the surgeon should be aware of the distinct roles of both layers (whether in the case of trauma or scheduled surgery) and make sure that the reconstruction plan will provide a favorable outcome.

Clinical, Biochemical, Radiological, Genetic and Therapeutic Analysis of Patients with COMP Gene Variants.

Pseudoachondroplasia (PSACH) and multiple epiphyseal dysplasia type 1 (MED1) are two rare skeletal disorders caused by cartilage oligomeric matrix protein (COMP) variants. This study aims to analyze the genotype and phenotype of patients with COMP variants. Clinical information for 14 probands was collected; DNA was extracted from blood for COMP variant detection. Clinical manifestations and radiology scoring systems were established to evaluate the severity of each patient's condition. Serum COMP levels in PSACH patients and healthy subjects were measured. Thirty-nine patients were included, along with 12 PSACH probands and two MED1 probands. Disproportionate short stature, waddling gait, early-onset osteoarthritis and skeletal deformities were the most common features. The height Z-score of PSACH patients correlated negatively with age at evaluation (r = - 0.603, p = 0.01) and the clinical manifestation score (r = - 0.556, p = 0.039). Over 50% of the PSACH patients were overweight/obese. The median serum COMP level in PSACH patients was 16.75 ng/ml, which was significantly lower than that in healthy controls (98.53 ng/ml; p < 0.001). The condition of MED1 patients was better than that of PSACH patients. Four novel variants of COMP were detected: c.874T>C, c.1123_1134del, c.1531G>A, and c.1576G>T. Height Z-scores and serum COMP levels were significantly lower in patients carrying mutations located in calmodulin-like domains 6, 7, and 8. As the two phenotypes overlap to different degrees, PSACH and MED1 are suggested to combine to produce "spondyloepiphyseal dysplasia, COMP type". Clinical manifestations and radiology scoring systems, serum COMP levels and genotype are important for evaluating patient condition severity.

Health-related Quality of Life in Adult Patients with Multiple Epiphyseal Dysplasia and Spondyloepiphyseal Dysplasia.

OBJECTIVES: Multiple epiphyseal dysplasia (MED) and spondyloepiphyseal dysplasia (SED) are skeletal dysplasias associated with premature osteoarthritis and short stature. Patients with SED often have spinal and ocular problems. Few reports have focused on the health-related quality of life (HRQoL) of patients with skeletal dysplasias associated with premature osteoarthritis. The purpose of this study was to evaluate the HRQoL of adult patients with MED and SED. METHODS: Questionnaires covering demographics, medical history (cataract, retinal detachment, and osteoarthritis), surgical history (osteotomy and arthroplasty), and the Short Form-36 (SF-36) health survey were sent to all patients with MED and SED with medical records at the investigators' institutions. Among the 27 patients who completed the questionnaire, patients aged 20 years or older were included in this cohort. RESULTS: The subjects were 18 affected individuals. The physical component summary score (PCS) was significantly lower in the MED and SED groups than in the normal population and tended to deteriorate with age. Conversely, there was a positive correlation between the mental component summary score and age. The role/social component summary score was not correlated with age. MED patients with osteoarthritis had a low PCS. PCS was particularly low in two SED patients with a medical history of cataract, whereas there was no association with a history of retinal detachment or osteoarthritis. CONCLUSIONS: The physical domain of HRQoL in MED and SED patients significantly deteriorated at a young age. Appropriate medical management of these skeletal dysplasias is required not only for orthopedic functions but also for ocular problems.

Massager-Induced Anterior Subcapsular Cataracts and Keratoconus in a Patient With Multiple Epiphyseal Dysplasia.

Multiple epiphyseal dysplasia (MED) is a phenotypically heterogeneous disease associated with orthopedic abnormalities among other systemic manifestations. While the spectrum of ocular abnormalities in this disorder is yet to be fully reported, MED has been rarely associated in the literature with the development of cataracts and keratoconus. Here, we report a case of bilateral massager-induced anterior subcapsular cataracts and keratoconus in a 46-year-old female with MED. This case presentation aims to prevent similar occurrences of inappropriate massaging device use and highlight potential ocular findings in MED patients.

SLC26A2-Associated Diastrophic Dysplasia and rMED-Clinical Features in Affected Finnish Children and Review of the Literature.

Diastrophic dysplasia (DTD) is a rare osteochondrodysplasia characterized by short-limbed short stature and joint dysplasia. DTD is caused by mutations in SLC26A2 and is particularly common in the Finnish population. However, the disease incidence in Finland and clinical features in affected individuals have not been recently explored. This registry-based study aimed to investigate the current incidence of DTD in Finland, characterize the national cohort of pediatric subjects with DTD and review the disease-related literature. Subjects with SLC26A2-related skeletal dysplasia, born between 2000 and 2020, were identified from the Skeletal dysplasia registry and from hospital patient registry and their clinical and molecular data were reviewed. Fourteen subjects were identified. Twelve of them were phenotypically classified as DTD and two, as recessive multiple epiphyseal dysplasia (rMED). From the subjects with available genetic data, 75% (9/12) were homozygous for the Finnish founder mutation c.-26+2T>C. Two subjects with rMED phenotype were compound heterozygous for p.Arg279Trp and p.Thr512Lys variants. The variable phenotypes in our cohort highlight the wide spectrum of clinical features, ranging from a very severe form of DTD to milder forms of DTD and rMED. The incidence of DTD in Finland has significantly decreased over the past decades, most likely due to increased prenatal diagnostics.

A unique case of skeletal dysplasia in an adult male in Late Iron Age Switzerland.

OBJECTIVE: We report a probable case of multiple skeletal dysplasia observed in a Late Iron Age young adult male. MATERIALS: The individual studied belongs to a Late Iron Age necropolis from Switzerland. The skeletal elements are well preserved METHODS: Macroscopic and radiographic assessment. RESULTS: The individual shows evidence of both craniofacial and mandibular deformation. Developmental defects are also visible with effects on the general shape and articular surfaces of both humeri, as well as the left femur and tibia. CONCLUSION: We propose that the lesions observed are manifestations of skeletal dysplasia, such as pseudo-achondroplasia or multiple epiphyseal dysplasia. SIGNIFICANCE: This is the first recorded case of multiple skeletal dysplasia in an Iron Age necropolis in Switzerland, questioning the integration of physically compromised individuals in La Tène society. LIMITATIONS: Examination of other skeletal dysplasias from archaeological contexts provides support for this diagnosis. SUGGESTIONS FOR FUTURE RESEARCH: The integration of individuals with disabilities in La Tène societies is still poorly understood and further research is needed to better characterize these communities.

Expanding the phenotypic spectrum of RPL13-related skeletal dysplasia.

RPL13-related disorder is a newly described skeletal dysplasia characterized as a form of spondyloepimetaphyseal dysplasia with normal birth length, early postnatal growth deficiency, severe short stature, and genu varum. We present a 9-year-old male with a history of lower leg pain and concern for an unspecified form of multiple epiphyseal dysplasia (MED). Exome sequencing revealed a de novo heterozygous RPL13 c.477+1G>A (IVS4+1G>A) pathogenic variant. This is the first identified case of an individual with an RPL13-related skeletal dysplasia, normal height, and radiographs consistent with a form of MED and Legg-Calve-Perthes-like disease. This case expands the phenotype of RPL13-related disorders.

Age Dependent Progression of Multiple Epiphyseal Dysplasia and Pseudoachondroplasia Due to Heterozygous Mutations in COMP Gene.

Dominantly inherited mutations in COMP gene encoding cartilage oligomeric matrix protein may cause two dwarfing skeletal dysplasias, milder multiple epiphyseal dysplasia (MED) and more severe pseudoachondroplasia (PSACH). We studied the phenotype and X-rays of 11 patients from 5 unrelated families with different COMP mutations. Whole exome and/or Sangers sequencing were used for molecular analyses. Four to ten X-ray images of hands hips, knees or spine were available for each patient for retrospective analyses. Eight patients with MED have mutation c.1220G>A and 3 children with PSACH mutations c.1359C>A, c.1336G>A, or the novel mutation c.1126G>T in COMP. Progressive failure in growth developed in all patients from early childhood and resulted in short stature < 3rd percentile in 7 patients and very short stature < 1st percentile in four. Most patients had joint pain since childhood, severe stiffness in shoulders and elbows but increased mobility in wrists. Six children had bowlegs and two had knock knees. In all patients, X-rays of hands, hips and knees showed progressive, age-dependent skeletal involvement more pronounced in the epiphyses of long rather than short tubular bones. Anterior elongation and biconvex configuration of vertebral bodies were more conspicuous for kids. Six children had correction of knees and two adults had hip replacement. Skeletal and joint impairment in patients with MED and PSACH due to COMP mutation start in early childhood. Although the clinical severity is mutation and age dependent, many symptoms represent a continuous phenotypic spectrum between both diseases. Most patients may benefit from orthopaedic surgeries.

Multiple occurrence of premature polyarticular osteoarthritis in an early medieval Bohemian cemetery (Prague, Czech Republic).

OBJECTIVES: To highlight conditions that may cause early-onset degenerative joint disease, and to assess the possible impact of such diseases upon everyday life. MATERIAL: Four adults aged under 50 years from a medieval skeletal collection of Prague (Czechia). METHODS: Visual, osteometric, X-ray, and histological examinations, stable isotope analysis of bone collagen. RESULTS: All four individuals showed multiple symmetrical degenerative changes, affecting the majority of joints of the postcranial skeleton. Associated dysplastic deformities were observed in all individuals, including bilateral hip dysplasia (n = 1), flattening of the femoral condyles (n = 3), and substantial deformation of the elbows (n = 3). The diet of the affected individuals differed from the contemporary population sample. CONCLUSIONS: We propose the diagnosis of a mild form of skeletal dysplasia in these four individuals, with multiple epiphyseal dysplasia or type-II collagenopathy linked to premature osteoarthritis as the most probable causes. SIGNIFICANCE: Combining the skeletal findings with information from the medical literature, this paper defines several characteristic traits which may assist with the diagnosis of skeletal dysplasia in the archaeological record. LIMITATIONS: As no genetic analysis was performed to confirm the possible kinship of the individuals, it is not possible to definitively assess whether the individuals suffered from the same hereditary condition or from different forms of skeletal dysplasia. SUGGESTIONS FOR FURTHER RESEARCH: Further studies on premature osteoarthritis in archaeological skeletal series are needed to correct the underrepresentation of these mild forms of dysplasia in past populations.

A novel COMP mutation in a Chinese family with multiple epiphyseal dysplasia.

BACKGROUND: Multiple epiphyseal dysplasia (MED) is a skeletal disorder characterized by delayed and irregular ossification of the epiphyses and early-onset osteoarthritis. At least 66% of the reported autosomal dominant MED (AD-MED) cases are caused by COMP mutations. METHODS: We recruited a four-generation Chinese family with early-onset hip osteoarthritis, flatfoot, brachydactyly, and mild short stature. An assessment of the family history, detailed physical examinations, and radiographic evaluations were performed on the proband and other family members, followed by the performance of whole-exome sequencing (WES). The pathogenicity of the candidate mutation was also analyzed. RESULTS: An AD-MED family with 10 affected members and 17 unaffected members was recruited. The main radiographic findings were symmetrical changes in the dysplastic acetabulum and femoral heads, irregular contours of the epiphyses, a shortened femoral neck, and flatfoot. Lower bone density was also observed in the ankle joints, wrist joints, and knees, as well as irregular vertebral end plates. In the proband, we identified the missense mutation c.1153G > T (p. Asp385Tyr), located in exon 11 of the COMP gene. This mutation was assessed as 'pathogenic' because of its low allele frequency and its high likelihood of co-segregation with disease in the reported family. Sanger sequencing validated the novel heterozygous mutation c.1153G > T (p. Asp385Tyr) in exon 11 of COMP in all affected individuals in the family. CONCLUSIONS: Our results underlined a key role of the Asp385 amino acid in the protein function of COMP and confirmed the pathogenicity of the COMP (c.1153G > T; p. Asp385Tyr) mutation in AD-MED disease. We have therefore expanded the known mutational spectrum of COMP and revealed new phenotypic information for AD-MED.

A novel p.A191D matrilin-3 variant in a Vietnamese family with multiple epiphyseal dysplasia: a case report.

BACKGROUND: Multiple epiphyseal dysplasia (MED) is a common skeletal dysplasia that is characterized by variable degrees of epiphyseal abnormality primarily involving the hip and knee joints. Mutations in a gene encoding matrilin-3 (MATN3) have been reported as disease causing of autosomal dominant MED. The current study identified a novel c.572 C > A variant (p.A191D) in exon 2 of MATN3 in a Vietnamese family with MED. CASE PRESENTATION: A standard clinical tests and radiological examination were performed in an 8-year-old Vietnamese girl patient. The clinical examination showed that patient height was under average, with bent lower limbs, limited mobility and dislocation of the joints at both knees. Radiological documentation revealed abnormal cartilage development at the epiphysis of the femur and patella. The patient has a varus deformity of the lower limbs. The patient was diagnosed with autosomal dominant MED using molecular testing in the order of the coding sequences and flanking sequences of five genes: COMP (exons 8-19), MATN3 (exon 2), COL9A2 (exon 3), COL9A3 (exon 3), COL9A1 (exon 8) by Sanger sequencing. A novel heterozygous missense variant (c.572 C > A, p.A191D) in MATN3 was identified in this family, which were not inherited from parents. The p.A191D was predicted and classified as a pathogenic variant. When the two predicted structures of the wild type and mutant matrilin-3 were compared, the p.A191D substitution caused conformational changes near the substitution site, resulting in deformity of the ß-sheet of the single A domain of matrilin- 3. CONCLUSIONS: This is the first Vietnamese MED family attributed to p.A191D matrilin-3 variant, and our clinical, radiological and molecular data suggest that the novel de novo missense variant in MATN3 contributed to MED.