Multiple epiphyseal dysplasias (MED/EDMs) are characterized by epiphyseal anomalies causing joint pain early in life, repeated osteochondritis and early arthrosis. The EMDs are a heterogeneous group of diseases with variable expression classed as MED/EMDs 1-6. The average prevalence is estimated at around 1/20,000. EDM1 (see this term) is clinically the best characterised form of EMD and is marked by a waddling gait and pain at onset, and moderate short stature. The main complication is early arthrosis of the hip. EDM1 is transmitted as an autosomal dominant trait and is caused by mutations in the gene (COMP; 19p13.1) encoding COMP (cartilage oligomeric matrix protein). Other dominantly inherited forms of EDM are not as well characterised clinically but causative mutations in genes encoding several cartilage extracellular matrix components have been identified in some cases: COL9A2 (1p33-p32.2) for EDM2, COL9A3 (20q13.3) for EDM3 and COL9A1 (6q13) for EDM6 (EDMs due to collogen 9 anomalies; see this term), and MATN3 (2p24-p23) for EDM5 (see this term). An atypical form of EDM (EDM4; see this term), characterized by club foot and double layered patella, has been reported and is transmitted as an autosomal recessive trait caused by mutations in the SLC26A2 gene (5q32-q33.1). Some forms of dysplasia are mainly limited to the femoral epiphyses (Meyer dysplasia; see this term). In addition, several syndromes characterized by the association of EDM with other clinical manifestations such as myopia, deafness and facial dysmorphism have also been described (see these terms). Diagnosis relies on identification of the radiological features. Current treatments involve mainly physiotherapy and orthopedic care. Hip replacement is frequently required, but the age at intervention is variable. *Author: Prof. M. Le Merrer (November 2008)*.