Clinical phenotype and molecular diagnosis of multiple epiphyseal dysplasia with relative hip sparing during childhood (EDM2)

We report on a family of 19 individuals over four generations in which 12 members are affected with a variant of multiple epiphyseal dysplasia. Beginning in childhood, the disease leads to pain and stiffness of knees, ankles, elbows and finger joints. Some adult patients repeatedly suffer from free articular bodies resulting in locking of the joint. Finally, affected individuals are prone to the development of early degenerative joint disease. Mutation screening of candidate regions revealed a novel point mutation at position -1 in the COL9A2 exon 3/intron 3 splicing region. This G-->C substitution most probably induces an alteration of the splicing process. Family screening was carried out by both automated sequencing and by digestion of amplicons with BsaWI. We confirmed the nucleotide substitution in eight clinically affected family members as well as in three presymptomatic young children. Electron microscopy showed that the diameter of collagen fibrils from arthroscopically removed free articular bodies of two patients was not obviously different from that of normal articular cartilage. Together with previous reports our results indicate that mutations leading to skipping of exon 3 within the COL3 domain of the alpha2-chain of collagen type IX may be relatively common in patients with a special subtype of multiple epiphyseal dysplasia (MED) in which the hips are not markedly affected at early age (EDM2). In these patients and their families, mutation screening of the candidate regions may help to confirm the diagnosis, lead to appropriate advice for lifestyle and well based genetic counseling. (C) 2002 Wiley-Liss, Inc.