Gender differences in ankylosing spondylitis patients: Relation to clinical characteristics, functional status and disease activity

Objective: To assess gender differences in Ankylosing Spondylitis (AS) patients regarding the clinical presentation, disease activity and functional status. Methods and findings: Forty AS patients; 21 males and 19 females, regularly following at the Rheumatology outpatient’s clinic, Saudi German Hospital, Riyadh, KSA were included. Functional status and the disease activity were evaluated using Bath Ankylosing Spondylitis Functional Index (BASFI) and the Bath AS Disease Activity Index (BASDAI) respectively. Mean age was 34.3 ± 8.5 years with a comparable sex ratio (M:F 1.11:1). Morning stiffness was markedly lower in females (72.4 ± 52.4 vs 112.9 ± 44.4 minutes) (p=0.01).Bilateral sacroiliitis was significantly more in males (n=18; 85.7% vs n=13; 68.4%) (p=0.02).The Schöber’s test was more limited and the finger-to-floor distance more increased in males (4.5 ± 0.8 cm and 40.7 ± 9.2 cm vs 4.9 ± 0.7 cm and 27.9 ± 9.7 cm; p=0.046 and p<0.001 respectively). Human leukocytic antigen-B27) was positive in 85.7% of males while rheumatoid factor was positive in only 3 females. BASFI showed significantly higher value in females (6.7 ± 1.1 vs 5.8 ± 1.4) (p=0.04), while BASDAI showed only a tendency to be higher in females. Using Magnetic resonance imaging of the sacroiliac joint, sacroiliitis was detected in all cases with signs of activity in 9 males and 7 females, erosions in 8 males and 5 females, effusion in 1 female and total ankylosis in 1 male. Conclusion: The clinical presentation and genetic background were more remarkable in the AS males; however the disease activity and functional impairment were increased in females. Radiological findings were comparable.Understanding the gender differences in AS may discern how this may impact future research, diagnosis and treatment.