Mutations in the known genes are not the major cause of MED; distinctive phenotypic entities among patients with no identified mutations

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.

Multiple epiphyseal dysplasia and related disorders: Molecular genetics, disease mechanisms, and therapeutic avenues

For the vast majority of the 6000 known rare disease the pathogenic mechanisms are poorly defined and there is little treatment, leading to poor quality of life and high healthcare costs. Genetic skeletal diseases (skeletal dysplasias) are archetypal examples of rare diseases that are chronically debilitating, often life-threatening and for which no treatments are currently available. There are more than 450 unique phenotypes that, although individually rare, have an overall prevalence of at least 1 per 4000 children. Multiple epiphyseal dysplasia (MED) is a clinically and genetically heterogeneous disorder characterized by disproportionate short stature, joint pain, and early-onset osteoarthritis. MED is caused by mutations in the genes encoding important cartilage extracellular matrix proteins, enzymes, and transporter proteins. Recently, through the use of various cell and mouse models, disease mechanisms underlying this diverse phenotypic spectrum are starting to be elucidated. For example, ER stress induced as a consequence of retained misfolded mutant proteins has emerged as a unifying disease mechanisms for several forms of MED in particular and skeletal dysplasia in general. Moreover, targeting ER stress through drug repurposing has become an attractive therapeutic avenue.

Exome sequencing reveals a novel COL2A1 mutation implicated in multiple epiphyseal dysplasia

Mutations in the COMP, COL9A1, COL9A2, COL9A3, MATN3, and SLC26A2 genes cause approximately 70% of multiple epiphyseal dysplasia (MED) cases. The genetic changes involved in the etiology of the remaining cases are still unknown, suggesting that other genes contribute to MED development. Our goal was to identify a mutation causing an autosomal dominant form of MED in a large multigenerational family. Initially, we excluded all genes known to be associated with autosomal dominant MED by using microsatellite and SNP markers. Follow-up with whole-exome sequencing analysis revealed a mutation c.2032G>A (p.Gly678Arg) in the COL2A1 gene (NCBI Reference Sequence: NM_001844.4), which co-segregated with the disease phenotype in this family, manifested by severe hip dysplasia and osteoarthritis. One of the affected family members had a double-layered patella, which is frequently seen in patients with autosomal recessive MED caused by DTDST mutations and sporadically in the dominant form of MED caused by COL9A2 defect.

Impact of Arginine to Cysteine Mutations in Collagen II on Protein Secretion and Cell Survival

Inherited point mutations in collagen II in humans affecting mainly cartilage are broadly classified as chondrodysplasias. Most mutations occur in the glycine (Gly) of the Gly-X-Y repeats leading to destabilization of the triple helix. Arginine to cysteine substitutions that occur at either the X or Y position within the Gly-X-Y cause different phenotypes like Stickler syndrome and congenital spondyloepiphyseal dysplasia (SEDC). We investigated the consequences of arginine to cysteine substitutions (X or Y position within the Gly-X-Y) towards the N and C terminus of the triple helix. Protein expression and its secretion trafficking were analyzed. Substitutions R75C, R134C and R704C did not alter the thermal stability with respect to wild type; R740C and R789C proteins displayed significantly reduced melting temperatures (T_m) affecting thermal stability. Additionally, R740C and R789C were susceptible to proteases; in cell culture, R789C protein was further cleaved by matrix metalloproteinases (MMPs) resulting in expression of only a truncated fragment affecting its secretion and intracellular retention. Retention of misfolded R740C and R789C proteins triggered an ER stress response leading to apoptosis of the expressing cells. Arginine to cysteine mutations towards the C-terminus of the triple helix had a deleterious effect, whereas mutations towards the N-terminus of the triple helix (R75C and R134C) and R704C had less impact.

The fate of hips that are conservatively treated in multiple epiphyseal dysplasia

We reviewed the radiologic and clinical outcomes of hip joints affected by multiple epiphyseal dysplasia in 40 patients. The average patient age was 9.6 years. All patients were followed up for an average of 7.2 years. No patient underwent surgical treatment. The variances of the center-edge angle and femoral head coverage had the greatest tendency to increase with conservative treatment and follow-up (P=0.011 and 0.015, respectively). The acetabular angle and the acetabular depth index at the first visit and the latest follow-up were statistically significantly different (P=0.046 and 0.027, respectively). According to the Stulberg classification, the severity of hip deformity became less severe with age, but this was not statistically significant (P=0.090). Larger improvements in Harris hip scores were identified after conservative treatment (P=0.003). Favorable midterm outcomes were obtained for the treatment of hip deformity in multiple epiphyseal dysplasia patients by conservative treatment.

Comparison of orthopaedic manifestations of multiple epiphyseal dysplasia caused by MATN3 versus COMP mutations: a case control study

Background

Multiple epiphyseal dysplasia (MED) is a relatively common skeletal dysplasia mainly involving the epiphyses of the long bones. However, it is a genetically heterogeneous group of diseases sharing certain aspects of the radiologic phenotype. In surveys conducted in East Asia, MATN3 was the most common causative gene, followed by COMP. In this study, the authors compared clinical manifestation of MED patients caused by MATN3 and COMP gene mutations, as well as subsequent orthopaedic interventions.

Methods

Fifty nine molecularly-confirmed MED patients were subjects of this study. The MATN3 gene mutation group comprised of 37 patients (9 female, 28 male). The COMP gene mutation consisted of 22 cases (15 females, 7 males). Medical records and radiographs were reviewed, and questionnaire surveys or telephone interviews were conducted.

Results

At the first presentation, the mean age was 8.8 ± 2.8 years (mean ± standard deviation) in the MATN3 group, and 8.5 ± 3.5 years in the COMP group (p = 0.670). The height in the COMP group was significantly shorter than those in the MATN3 group (p < 0.001). Gait abnormality at the first visit (p = 0.041) and the lastest follow-up (p = 0.037) were statistically significant difference. Hip pain (p = 0.084), limitation of daily activity (p = 0.075) at the latest follow-up tended to be more frequent in the COMP group. Hip dysplasia was more common in the COMP group, having significantly larger acetabular angle (p = 0.037), smaller center-edge angle (p = 0.002), severe Stulberg classification (p < 0.001), and smaller femoral head coverage (p < 0.001).

Conclusions

Clinical manifestations of MED caused by MATN3 were milder than manifestations of the COMP mutation group. These differences in clinical manifestation and prognosis justify molecular differentiation between the two genotypes.

Pseudoachondroplasia and multiple epiphyseal dysplasia: a 7-year comprehensive analysis of the known disease genes identify novel and recurrent mutations and provides an accurate assessment of their relative contribution

Pseudoachondroplasia (PSACH) and multiple epiphyseal dysplasia (MED) are relatively common skeletal dysplasias resulting in short-limbed dwarfism, joint pain, and stiffness. PSACH and the largest proportion of autosomal dominant MED (AD-MED) results from mutations in cartilage oligomeric matrix protein (COMP); however, AD-MED is genetically heterogenous and can also result from mutations in matrilin-3 (MATN3) and type IX collagen (COL9A1, COL9A2, and COL9A3). In contrast, autosomal recessive MED (rMED) appears to result exclusively from mutations in sulphate transporter solute carrier family 26 (SLC26A2). The diagnosis of PSACH and MED can be difficult for the nonexpert due to various complications and similarities with other related diseases and often mutation analysis is requested to either confirm or exclude the diagnosis. Since 2003, the European Skeletal Dysplasia Network (ESDN) has used an on-line review system to efficiently diagnose cases referred to the network prior to mutation analysis. In this study, we present the molecular findings in 130 patients referred to ESDN, which includes the identification of novel and recurrent mutations in over 100 patients. Furthermore, this study provides the first indication of the relative contribution of each gene and confirms that they account for the majority of PSACH and MED.

New intermediate phenotype between MED and DD caused by compound heterozygous mutations in the DTDST gene

DTDST mutations cause a spectrum of diastrophic dysplasia disorders characterized by defects of proteoglycans sulfation. Reduction of sulfate/chloride antiporter activity is manifested by lower sulfate uptake and depends on a combination of mutations in DTDST. We analyzed a family with an autosomal recessive form of bone dysplasia. Three affected brothers from this family are compound heterozygotes for C653S/A715V mutations. We classified their phenotype as a new intermediate form between diastrophic dysplasia and multiple epiphyseal dysplasia, manifested by shortening of stature, metatarsus adductus/club foot, mild brachydactyly, proximally placed thumbs and clinodactyly of the fifth fingers. Radiographs document platyspondyly most marked in the lower thoracic and upper lumbar spine, epiphyseal dysplasia affecting predominantly the femoral heads, widening of the metaphyses, narrow growth cartilage and multilayered patellae. Exaggerated lesser trochanters of femur, that is, "monkey wrench" sign, elevated greater trochanters, thin upper pubic rami, grossly normal carpal/tarsal bones and severe, early onset osteoarthritis were other notable features.

Autosomal recessive multiple epiphyseal dysplasia in a Korean girl caused by novel compound heterozygous mutations in the DTDST (SLC26A2) gene

Multiple epiphyseal dysplasia is caused by heterogeneous genotypes involving more than six genes. Recessive mutations in the DTDST gene cause a phenotype of recessive multiple epiphyseal dysplasia (rMED). The authors report a 9-yr old Korean girl with the rMED phenotype having novel compound heterozygous mutations in the DTDST gene, which were inherited from both parents. This is the first Korean rMED case attributed to DTDST mutations, and expands the spectrum of diseases caused by DTDST mutations.

Multiple epiphyseal dysplasia

BACKGROUND

Multiple epiphyseal dysplasia (MED) is a common genetically and clinically heterogeneous skeletal dysplasia characterized by early-onset osteoarthritis, mainly in the hip and knee, and mild-to-moderate short stature. Here we report on a 6-generation MED family with 17 affected members.

METHOD

The clinical and radiographic data on the 12 affected members still living were scrutinized. A structured inquiry comprising state of health and MED-related symptoms since birth up to the present time and the osteoarthritis outcome (KOOS) questionnaire were sent to all living family members with MED. The 5 known gene loci for autosomal dominant MED were analyzed for linkage, using fluorescence-labeled microsatellite markers. Linkage was ascertained with markers close to the COL9A2 gene, which was analyzed for mutations by sequencing.

RESULTS

We identified an exon 3 donor splice mutation in the COL9A2 gene in all affected family members. Clinical, radiographic, and questionnaire data from affected family members suggested that MED caused by COL9A2 mutations starts in early childhood with knee pain accompanied by delayed ossification of femoral epiphyses. The disease then either stabilizes during puberty or progresses with additional joints becoming affected; joint surgery might be necessary. The progression of the disease also affects muscles, with increasing atrophy, resulting in muscle fatigue and pain. Muscular atrophy has not been reported earlier in cases with COL9A2 mutations.

INTERPRETATION

In a patient with clinically suspected or verified MED, it is important to perform DNA-based analysis to identify a possible disease-causing mutation. This information can be used to carry out genetic risk assessment of other family members and to achieve an early and correct diagnosis in the children.

Multilayered patella: similar radiographic findings in pseudoachondroplasia and recessive multiple epiphyseal dysplasia

A multilayered patella is a characteristic radiographic finding of recessive multiple epiphyseal dysplasia (rMED) caused by DTDST mutations. However it has been recently reported in a dominant MED case with a COL9A2 mutation. We report on a new radiographic patellar finding in a patient with pseudoachondroplasia and a heterozygous COMP mutation. It is similar to the radiographic appearance of fusing multilayered patellae in rMED cases. This led us to search the International Skeletal Dysplasia Registry for similar abnormalities. We did not observe this finding in other skeletal dysplasias or other pseudoachondroplasia cases. However we found an accessory ossification center of the patella in another pseudoachondroplasia case. Thus, we hypothesize that variable defects of cartilage extracellular matrix can result in similar abnormal patellar ossifications, and emphasize the importance of a lateral knee radiograph in patients with the pseudoachondroplasia-MED bone dysplasia group of disorders.

Clinical, radiographic, and pathologic abnormalities in dogs with multiple epiphyseal dysplasia: 19 cases (1991-2005)

OBJECTIVE

To determine clinical, radiographic, and pathologic abnormalities in dogs with multiple epiphyseal dysplasia (MED).

DESIGN

Retrospective case series.

ANIMALS

19 dogs with MED from 10 litters.

PROCEDURES

The diagnosis was made on the basis of radiographs of the shoulder region and vertebral column. Ten dogs underwent necropsy.

RESULTS

There were 11 Hygenhund, 6 Dunker, 1 Golden Retriever, and 1 English Pointer. Most dogs were examined because of lameness that developed at 5 to 8 months of age. The most common radiographic abnormality was a deficiency in ossification of the epiphyses, apophyses, and cuboidal bones of the appendicular skeleton and the epiphyses of the vertebrae; ossification of the metaphyses and the diaphyses typically were normal. Disease severity was consistent among littermates, but varied among dogs from different litters.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that MED is a rare condition in dogs characterized by a deficiency in ossification of the epiphyses of the long bones, the epiphyses of the vertebrae, the cuboidal bones, and the apophyses. Radiographic abnormalities were evident in dogs examined as young as 8 weeks of age, and most dogs had developed severe lameness by 5 to 8 months of age. The condition most likely had an autosomal recessive mode of inheritance, although genetic studies of mode of inheritance could not be performed.

Skeletal dysplasia presenting as a neuromuscular disorder - report of three children

Three pediatric patients were investigated because of suspected muscle disorder. They were clumsy with an awkward looking waddling gait and had increasing muscle weakness and pain in the legs. Serum CK-values, electroneuromyography (ENMG) and muscle biopsy were all normal. A post-traumatic X-ray of the ankle of one of them showed epiphyseal changes and his condition was diagnosed as Camurati-Engelmann disease. Because of similarities in the clinical presentation of these boys, bone changes were looked for in the two other patients and a diagnosis of multiple epiphyseal dysplasia was made. Skeletal dysplasia should be considered as a diagnostic alternative when a child presents with an unexplained muscle weakness accompanied with pain in the limbs. Specific treatment for bone dysplasias can alleviate symptoms and prevent fractures.

Preselection of cases through expert clinical and radiological review significantly increases mutation detection rate in multiple epiphyseal dysplasia

Skeletal dysplasias are difficult to diagnose for the nonexpert. In a previous study of patients with multiple epiphyseal dysplasia (MED), we identified cartilage oligomeric matrix protein (COMP) mutations in only 36% of cases and suspected that the low-mutation detection rate was partially due to misdiagnosis. We therefore instituted a clinical-radiographic review system, whereby all cases were evaluated by a panel of skeletal dysplasia experts (European Skeletal Dysplasia Network). Only those patients in whom the diagnosis of MED was confirmed by the panel were screened for mutations. Under this regimen the mutation detection rate increased to 81%. When clinical-radiological diagnostic criteria were relaxed the mutation rate dropped to 67%. We conclude that expert clinical-radiological review can significantly enhance mutation detection rates and should be part of any diagnostic mutation screening protocol for skeletal dysplasias.

Genetic analysis of skeletal dysplasia: recent advances and perspectives in the post-genome-sequence era

Skeletal dysplasia is a group of disorders of the skeleton that result from derangement of growth, development and/or differentiation of the skeleton. Nearly 300 disorders are included; most of them are monogenic diseases. Responsible genes for skeletal dysplasia have been identified in more than 150 diseases mainly through positional cloning. Identification of disease genes would improve patient care through genetic diagnosis as well as improving our understanding of the diseases and molecular mechanism of skeletal tissue formation. Studies of skeletal dysplasia would also help identify disease genes for common diseases affecting bones and joints. In this study, the author reviews recent advances and the current status of the genetic analysis of skeletal dysplasia and its impacts on research into skeletal biology.

Intrafamilial phenotypic diversity in multiple epiphyseal dysplasia associated with a COL9A2 mutation (EDM2)

We describe a Japanese family with an autosomal dominant multiple epiphyseal dysplasia (MED EDM2) showing significant phenotypic diversity among the five affected members. Genomic analysis for COL9A2 identified an Ex3-1A>G heterozygous mutation, which has been proved to result in skipping of exon 3. The proband was a 9-year-old boy, who presented with ulnar club hands due to severe epiphyseal dysplasia in the distal ulnae. Radiological examination showed multiple epiphyseal dysplasias, predominantly involving the knee and the wrist. The hip appeared almost normal. The malalignment of the wrist was successfully treated with a limb lengthening procedure. The phenotype of the asymptomatic 12-year-old brother was similar to, but milder than, that of the proband. The asymptomatic 39-year-old mother, the 35-year-old uncle, and the 65-year-old grandmother with bilateral painful knees showed radiographically mild and severe osteoarthritis of the knee, respectively, and none of them had wrist deformity.

Comprehensive screening of multiple epiphyseal dysplasia mutations in Japanese population

Multiple epiphyseal dysplasia (MED) is among the most genetically heterogeneous skeletal dysplasias. Six genes involved in MED, COMP, MATN3, COL9A1, COL9A2, COL9A3, and DTDST have been identified; however, the presence of additional disease genes has been reported, and the detection rate for mutations in known genes accounts for no more than 50% of patients with MED in Western populations. Here, we screened the six known disease genes in 35 consecutive Japanese MED patients. We analyzed the entire coding region of each gene, along with flanking intron-exon junctions, by direct sequencing. A total of 19 mutations were identified in COMP, MATN3, COL9A2, COL9A3, and DTDST. The detection rate for known mutations was higher in this study than in previous reports, and we identified a substantially different spectrum of mutations. Mutations in MATN3 were more prevalent among these Japanese patients, whereas no DTDST mutations were detected. Most of the mutations were localized within specific regions of each gene: COMP mutations were found in the calmodulin-like repeat domains; MATN3 mutations in the von Willebrand factor type A domain; and type IX collagen gene mutations occurred in the third collagenous domains. Based on the integration of clinical and genetic information, we propose an algorithm for detecting mutations in Japanese MED patients. Our study further supports the existence of additional MED gene(s).