Different Contributions of CDKAL1, KIF21B, and LRRK2/MUC19 Polymorphisms to SAPHO Syndrome, Rheumatoid Arthritis, Ankylosing Spondylitis, and Seronegative Spondyloarthropathy

Objectives: Synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome, rheumatoid arthritis (RA), ankylosing spondylitis (AS), and seronegative spondyloarthropathy (SPA) are autoimmune diseases of unknown etiology, which share some clinical manifestations in common. Previous family-based investigations support genetic contributions to the susceptibility of these diseases. The current study evaluated whether three previously reported AS-associated single-nucleotide polymorphisms (SNPs), rs6908425 T>C in CDKAL1, rs11584383 T>C near KIF21B, and rs11175593 C>T near LRRK2/MUC19, have any genetic overlap across multiple autoimmune diseases including SAPHO syndrome, RA, AS, and SPA. Materials and Methods: Genomic DNA was obtained from 71 SAPHO, 125 RA, 67 AS, and 35 SPA Han Chinese patients, as well as 104 healthy controls. SNPs were genotyped by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Genotype and allele frequencies were analyzed using the chi-square test. Results: rs6908425 T>C in CDKAL1 was significantly different between SAPHO cases and healthy controls (odds ratios = 2.056, 95% confidence intervals: 1.211-3.490; p = 0.007), but no SNPs were associated with the risk of developing RA, AS, or SPA (p > 0.05). Analysis of genotype distributions showed similar results. A significant difference was only found in the genotype frequency of rs6908425 in SAPHO cases (p = 0.004); no significant differences were detected among patients with RA, AS, and SPA (p > 0.05). Conclusions: Our results suggest that rs6908425 in CDKAL1 is associated with the risk of developing SAPHO in Han Chinese populations. People who carry the risk allele T of rs6908425 might be more prone to developing SAPHO syndrome.