Lack of relevance of the acetylator status on dapsone response in chronic autoimmune thrombocytopenic purpura

Dapsone provides an alternative treatment for patients with chronic autoimmune thrombocytopenic purpura (AITP) who had inadequate response to conventional therapy. However, the efficacy of this treatment is achieved in only 50% of patients. Dapsone is partly metabolized by the polymorphic N-acetyltransferase 2% and 50% of Caucasian patients show a genetically determined slow acetylator phenotype, The aim of our study was to investigate the influence of the acetylator status on dapsone efficacy in patients with chronic AITP, Nineteen caucasian adults with chronic AITP, previously treated by dapsone, were included in the study, Acetylator phenotype was determined by using a caffeine urinary test. Among the fourteen fast acetylator patients, eight patients exhibited positive response to dapsone and six patients did not. Among the five slow acetylator patients, one patient displayed a positive response to dapsone, Comparison of data by using the Fisher's exact test did not reach statistical significance, Our results do not support a relationship between dapsone efficacy and acetylator status in adults with chronic AITP. (C) 1999 Wiley-Liss, Inc.