The Role of Genetic Variation in Thiopurine Methyltransferase Activity and Efficacy and/or Side Effects of Azathioprine Therapy in Dermatologic Patients

Snow and Gibson¹ should be congratulated for their article in the February 1995 issue of the Archives that highlighted the interindividual variation in azathioprine metabolism in dermatologic patients. We were interested to observe how closely the conclusions of this study conformed to our previous predictions.² There are, however, a number of points that merit comment. The first study to have investigated the variable response to azathioprine by the measurement of the active nucleotide metabolites in dermatologic patients was published by one of us (L.L.) in 1987 and concerned four patients with pemphigus vulgaris.³ This was followed 2 years later by a more detailed study in which two of five study patients and the majority of the control group of 16 patients were dermatologic patients (for reasons of expediency rather than any particular interest in studying dermatologic patients).⁴ It would, of course, be misleading to imply that