Serum or plasma cartilage oligomeric matrix protein concentration as a diagnostic marker in pseudoachondroplasia: Differential diagnosis of a family

Abstract

Pseudoachondroplasia (PSACH) is an autosomal-dominant osteochondrodysplasia due to mutations in the gene encoding cartilage oligomeric matrix protein (COMP). Clinical diagnosis of PSACH is based primarily on family history, physical examination, and radiographic evaluation, and is sometimes extremely difficult, particularly in adult patients. Genetic diagnosis based on DNA sequencing, on the other hand, can be expensive, time-consuming, and intensive because COMP mutations may be scattered throughout the gene. However, there is evidence that decreased plasma COMP concentration may serve as a diagnostic marker in PSACH, particularly in adult patients. Here, we report the serum and/or plasma COMP concentration-based differential diagnosis of a family with affected adult members. The mean serum and/or plasma COMP concentrations of the three affected family members alive (0.69 ± 0.15 and/or 0.81 ± 0.08 µg/ml, respectively) were significantly lower than those of an age-compatible control group of 21 adults (1.52 ± 0.37 and/or 1.37 ± 0.36 µg/ml, respectively; P < 0.0001). Bidirectional fluorescent DNA sequencing-based genetic diagnosis of these patients revealed a heterozygous mutation for the nucleotide change 1532A > G in exon 14 of the COMP gene, resulting in a substitution of amino acid 511 from aspartic acid to glycine in COMP. Thus, serum and/or plasma COMP concentration may be suggested as an additional diagnostic marker to aid clinical and radiographic findings in suspected cases of PSACH.