Identification of nine novel mutations in cartilage oligomeric matrix protein in patients with pseudoachondroplasia and multiple epiphyseal dysplasia.

Pseudoachondroplasia (PSACH) and multiple epiphyseal dysplasia (EDM1) are allelic disorders caused by mutations in the gene encoding cartilage oligomeric matrix protein (COMP). PSACH is a dominant condition characterized by disproportionate short stature, joint laxity, and early-onset osteoarthritis. EDM1 is a less severe skeletal dysplasia associated with average to mild short stature, joint pain, and early-onset osteoarthritis. COMP is an extracellular matrix protein present in cartilage, ligament, and tendon tissues. Here, we report on nine novel mutations in COMP causing PSACH and EDM1. Four of these mutations are in exons 13C and 14 where no previous mutations had been reported. One of those mutations was identified in two separate EDM1 families. In addition, we have identified the first case of PSACH resulting from an expansion of the five aspartates in exon 17B. We are also reporting a mutation in a third PSACH family with somatic/germline mosaicism. Therefore, this report increases the range of mutations that cause PSACH and EDM1 and provides additional regions to target for mutational analysis.