The British journal of dermatology
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The present study was undertaken on the hypothesis that methaemoglobin production and haemolytic anaemia following dapsone administration could be ascribed to an impairment of glucose-6-phosphate dehydrogenase-enzymatic activity. Analysis of the kinetic parameters of the G-6-PD (Vmax and KM) was performed in ten patients, normal with respect to G-6-PD, suffering from various dermatoses. It was concluded that haemolytic anaemia after dapsone therapy is not due to a functional impairment of the enzyme. The close relationship between dapsone dosage, methaemoglobin production and anaemia make reasonable the hypothesis that a toxic dapsone derivative (DDS-NHOH) could be responsible for the methaemoglobin formation and the haemolytic anaemia.