In a cross-sectional controlled study, 147 AS patients and 121 controls underwent examinations, including demographic variables, laboratory (C-reactive protein (CRP), erythrocyte sedimentation rate (ESR)) and clinical measures (disease activity (AS disease activity score, ASDAS), physical function (Bath ankylosing spondylitis functional index, BASFI), spinal mobility (Bath ankylosing spondylitis metrology index, BASMI), chest expansion, cardio-respiratory fitness (peak oxygen uptake, VO2peak) and pulmonary function test (PFT) (spirometry)). The gene discussed is CRP; the disease is ankylosing spondylitis.