Primary ankylosing spondylitis: patterns of disease in a Brazilian population of 147 patients.

OBJECTIVE: To analyze patterns of disease in a population of Brazilian patients with primary ankylosing spondylitis (AS).
METHODS: Retrospective study (1988-98) analyzing 147 patients with a diagnosis of primary AS according to the modified New York criteria. Selected patients had complete clinical (initial symptom, axial and peripheral involvement, heel enthesitis, extraarticular manifestations) and radiological (sacroiliac, lumbar, thoracic, and cervical spine) investigations, and these data were compared with sex, race, age at onset, and HLA-B27.
RESULTS: There was a predominance of men (84.4%), Caucasian race (75.5%), adult onset (> 16 years, 85%), and positive HLA-B27 (78.2%). Family history of AS was noted in 14.3% of the patients. Pure axial AS was observed in 37 patients (25.2%). The predominant initial symptoms were inflammatory low back pain (61.9%) and peripheral arthritis (22.4%). Thoracic and cervical spine involvement was noted in 70.1% of the patients; radiological findings included syndesmophytes in 46.9% and "bamboo spine" in 20.4% of patients. The extraaxial joints most frequently involved were: ankles (39.5%), hips (36.1%), knees (29.3%), shoulders (19%), and sternoclaviculars (14.3%); heel enthesitis was present in 22.4%. Acute anterior uveitis was noted in 14.3% of patients. Male sex was associated with involvement of thoracic spine (p = 0.002), cervical spine (p = 0.002), and hips (p = 0.042), whereas female sex was associated with sternoclavicular (p = 0.024) involvement. Caucasian race presented higher frequency of positive family history (p = 0.023); there was no statistical significance of clinical and radiological variables compared with African-Brazilians. Juvenile onset AS presented higher frequency of ankle (p = 0.012) and knee (p = 0.001) involvement, heel enthesitis (p = 0.001), and total hip replacement (p = 0.038), whereas adult onset was associated with thoracic (p = 0.026) and cervical spine (p = 0.026) involvement and positive family history (p = 0.044). Positive HLA-B27 was associated with ankle involvement (p = 0.007) and heel enthesitis (p = 0.013).
CONCLUSION: In this population women showed a milder axial involvement, Caucasian race presented axial and peripheral involvement similar to African-Brazilians, juvenile onset AS was associated with articular involvement of the lower limbs, and positive HLA-B27 was associated with ankle involvement.