Multiple Epiphyseal Dysplasia

What does the name mean?

'Epiphysis' refers to the ends of long bones that are adjacent to the joints. Therefore, this disorder is one that involves more than one epiphysis.

How common is multiple epiphyseal dysplasia?

MED occurs in approximately 9 in 100,000 live births (4). Initially, two types of MED were identified: Fairbank Type (severe) and Ribbing Type (mild). However, the MED in now considered one clinically heterogenous disorder, and the two classifications have been abandoned (5).

How is multiple epiphyseal dysplasia inherited?

MED is typically inherited in an autosomal dominant manner (2). However, an autosomal recessive form of MED has also been idenitified (2). Due to non-allelic mutations, genetic heterogeneity does occur, resulting in a wide variability of expression.

What causes multiple epiphyseal dysplasia?

The Fairbank type of MED is caused by a mutation in the gene encoding the cartilage oligomeric matrix protein,’ or COMP. A less severe form can be caused by point mutations in any three of the type IX collagen genes (COL9A1, COL9A2, COL9A3). Type IX collagen is found on the surface of type II collagen and is necessary for the integrity of articular cartilage. Another mutation in the gene that encodes matrilin-3 causes a distinctively mild form of MED. Finally, the autosomal recessive form of MED is caused by mutations in the diastrophic dysplasia sulfate transporter (DTDST) gene or by mutations in the solute carrier family 26, member 2 gene (SLC26A2). Overall, the mutations result in a retarded formation of epiphyseal ossification centers. The bones most commonly affected are the humeraland femoral heads. Bones of the pelvis, spinal column and skull are typically normal.

• What are the physical characteristics of Multiple Epiphyseal Dysplasia?
• How is the diagnosis made?
• Problems in the musculoskeletal system
• Problems elsewhere in the body
• What are things to watch out for?
• References