Introduction: Ankylosing spondylitis (AS), the most common and severe form of spondyloarthritis, remains poorly documented in sub-Saharan Africa in terms of its clinical presentation and progression. This study aims to describe the epidemiological, clinical, therapeutic, and prognostic profiles of AS within the rheumatology unit of the National Hospital of Zinder (Niger). Methods: This was a longitudinal descriptive study with retrospective and prospective data collection, conducted over 54 months (July 2020 - February 2025) in the rheumatology unit of the Zinder National Hospital. All patients meeting the modified New York criteria for ankylosing spondylitis (AS) were included exhaustively. BASDAI and BASFI scores were assessed at baseline and at 3 months; their evolution was compared using the Wilcoxon signed-rank test for paired groups. Results: A total of 372 patients were included out of 5620 consultations, representing a hospital frequency of 6.62%. The mean age was 47.75 years ± 13.01 years (range: 17 - 85 years). There was a female predominance (72.58%; male-to-female ratio = 0.38). The median diagnostic delay was 52 months [Q25 - Q75: 25 - 125 months]. Pelvic pain was the main reason for consultation (66.40%). Peripheral involvement was present in 55.91% of patients, enthesitis in 27.69%, and uveitis in 5.65%. Radiological sacroiliitis was noted in all patients (Forrestier stage 2: 76.34%; stage 3: 22.04%; stage 4: 1.61%), and structural lesions of the lumbar spine in 88.71%. Therapeutically, NSAIDs were prescribed in 94.09% of patients, methotrexate in 36.29%, and sulfasalazine in 27.96%. At 3 months, the BASDAI score decreased significantly from 5.17 ± 2.69 to 3.09 ± 1.79 (Δ = ？2.08; p < 0.001), and the BASFI score decreased significantly from 5.30 ± 2.68 to 3.15 ± 1.91 (Δ = ？2.15; p < 0.001). Conclusion: Ankylosing spondylitis (AS) in Niger is characterized by a marked female predominance, frequent peripheral involvement, significant diagnostic delays, and advanced structural lesions at the time of diagnosis. However, a statistically significant and substantial improvement in disease activity and physical function was observed at 3 months with conventional management.
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