Prevalence of subclinical amyloidosis in ankylosing spondylitis

Abstract

OBJECTIVE: To study the prevalence of secondary amyloidosis in Indian patients with ankylosing spondylitis (AS). METHODS: Seventy-two AS patients with disease duration of more than 5 years were included in this study over a period of one and a half years. Abdominal subcutaneous fat pad aspiration (ASFA) was performed with a fine needle, and smears were examined for apple-green birefringence under polarized light after Congo red staining. The amyloid deposits were graded from 1+ to 3+ by visual inspection. Clinical and laboratory features of the patients were correlated with the absence or presence of amyloid deposits. RESULTS: Five patients (6.9%) with AS were positive for amyloid on ASFA. All the patients had 1+ deposit and were male. None of the patients had clinical amyloidosis. ASFA positive patients had a trend towards older age, longer disease duration, more limitation of the spinal mobility, and significantly lower hemoglobin levels. CONCLUSION: We found in our population that subclinical amyloid deposits can be detected in 7% of AS patients with disease duration longer than 5 years. There is a need to follow up patients with positive ASFA tests to check for the development of clinical amyloid.