Kidney and anemia in familial amyloidosis type I

BACKGROUND: Familial amyloid polyneuropathy (FAP) type I is caused by a mutated transthyretin (TTR V30M) and characterized by a sensorimotor and autonomic neuropathy. Renal, cardiac, and ocular abnormalities can also occur. Anemia has been described in previous reports, but its prevalence in Portuguese FAP patients is not precisely known. The aim of this study was to estimate the prevalence of anemia in FAP type I Portuguese patients and to evaluate the contribution of erythropoietin (Epo) to its genesis. METHODS: A retrospective cross-sectional study was undertaken to determinate the prevalence and characteristics of anemia in 165 FAP patients. For comparison analysis, 3 control groups were also evaluated, 1 group of 46 apparently healthy subjects, 1 group of 17 asymptomatic carriers of FAP-trait, and a group of 14 non-FAP patients with chronic renal insufficiency. Serum Epo levels were analyzed in all groups. RESULTS: Anemia was present in 24.8% of symptomatic FAP patients. Iron stores, B12 vitamin, and serum folate levels were normal. FAP patients presented significantly lower serum Epo levels than healthy controls (P= 0.003). Epo levels were found lower than expected for the degree of anemia and in 17.5% were undetectable. Low Epo values were observed independently of the presence of renal failure or anemia, and sometimes preceded clinical disease. CONCLUSION: Anemia in FAP type I is a common manifestation. The results clearly suggest a defective endogenous Epo production in the genesis of the anemia.