Renal amyloidosis in ankylosing spondylitis: A monocentric study and review of literature

Secondary renal amyloidosis (RA) is the most common type of renal involvement in ankylosing spondylitis (AS). We assessed the epidemiologic and clinico-biological profile of AS patients with RA, to analyze treatment modalities and prognostic aspects, and to determine predictive factors of RA during AS. This was a retrospective study including 13 cases of RA among 212 cases who presented with AS, during the period from 1978 to 2006. The median age of the patients at the time of diagnosing AS was 47 years (range: 19–67). There were 11 males and two females. RA onset was diagnosed after a mean follow-up of 144.6 months (range: 10–505) from the AS diagnosis. We noted erosive peripheral arthritis, lumbar stiffness with bamboo spine, and coxitis in 23.1%, 76.9%, and 30.8% of cases, respectively. Nephrotic syndrome was found in eight patients (61.5%). At the time of diagnosing RA, six patients had renal failure. Amyloid deposits were histologically proven by salivary gland biopsy in six cases (46.1%) and by renal biopsy in seven cases (53.8%). Four patients received a long-course treatment with colchicine but with a good outcome only in two cases. In our series, AS was more severe among patients with RA. Four predictive factors of RA were identified: smoking (P = 0.04), erosive peripheral arthritis (P = 0.002), bamboo spine (P = 0.001), and biologic indicators of inflammation (P = 0.0001). High erythrocyte sedimentation rate was identified as the only independent risk factor of RA during AS (P = 0.0001). Renal function as well as urinalysis should be monitored at regular intervals to detect early renal involvement during AS.