Phenotypic differences between familial versus sporadic ankylosing spondylitis: a cross-sectional Spanish registry of spondyloarthropathies (REGISPONSER).

Objectives: To analyse potential differences in disease phenotype between patients with familial ankylosing spondylitis (AS) and sporadic AS.
Methods: A cross-sectional study was conducted on all patients with definite AS registered at the internet database REGISPONSER. Sociodemographic data, clinical features, spinal mobility measurements, the Bath AS disease activity index (BASDAI), functional index (BASFI) and radiology index (BASRI), laboratory data (ESR, CRP, HLA-B27), overall patient assessment of the disease (VAS), and treatments used were obtained. Familial AS was considered when the patient was confirmed to have first-degree relatives with spondyloarthropathy. The Chi-square test and Mann-Whitney U-test were used for the statistical analysis.
Results: A total of 1316 AS patients (990 males, 326 females; mean age 48.2 ± 12.6 years), with mean age at symptom onset 26.1 ± 8.5 years, were evaluated. The prevalence of familial AS was 20% (n=263). Familial and sporadic AS groups presented differences (p<0.05) in the following parameters: female (34.6% vs. 22%), mean age at symptom onset (25.0±9.2 years vs. 27.3 ± 10.0 years), disease duration (23 ± 13 years vs. 21 ± 12 years), uveitis (27.5% vs. 19.3%), presence of HLA-B27+ (93% vs. 83%), VAS for overall patient assessment (5.0 cm vs. 4.4 cm), BASDAI (4.4 cm vs. 4.0 cm) and response to NSAID (82% vs. 74%).
Conclusions: Patients with familial AS were younger at symptom onset and had poorer VAS for overall patient assessment and BASDAI than the other group. There was a higher prevalence of females, uveitis, positive HLA-B27, hip prostheses and a better response to NSAID in the familial AS group.