Radiologic phenotypes in lumbar MR imaging for a gene defect in the COL9A3 gene of type IX collagen

PURPOSE: To evaluate whether the COL9A3 tryptophan allele (Trp3 allele) is associated with a specific radiologic phenotype among patients with sciatica. MATERIALS AND METHODS: One hundred fifty-three patients with sciatica were evaluated for the presence of Trp3 allele, Scheuermann disease, intervertebral disk degeneration, Schmorl nodules, dorsal anular tears, hyperintense lesions, and end-plate degeneration on sagittal T2-weighted lumbar magnetic resonance images. The Trp3 genotype was determined by means of sequencing the COL9A3 gene. Radiologic phenotypes were evaluated while blinded to the genotype. Scheuermann disease was diagnosed if either endplate irregularities or Schmorl nodules and two of the other three criteria (disk space narrowing, disk dehydration, and wedging of anterior vertebral body margins) were present at three or more adjacent disk levels from T10-11 to L3-4. Disk degeneration was evaluated separately for each disk (T11-12 to L5-S1) and for all disks combined. Frequencies of radiologic phenotypes between individuals with or without Trp3 allele were compared. RESULTS: Thirty-four patients had at least one Trp3 allele. When compared with the matched control subjects, they had an increased likelihood of Scheuermann disease (P=.035) and an increased number of degenerated disks from T11 to S1 (P=.021). Comparisons at individual disks showed a statistically significant increase in disk degeneration at T11-12 (analysis of all grades of degeneration [graded], P=.018; analysis of any degeneration vs none [dichotomous], P=.039) and L4-5 (graded, P=.011; dichotomous, P=.016). Prevalences of anular tears, endplate degeneration, Schmorl nodules, and hyperintense lesions were comparable. CONCLUSION: The results of this study indicate that the presence of Trp3 allele is associated with Scheuermann disease and intervertebral disk degeneration. No associations were found for other radiologic phenotypes. (C) RSNA, 2003.