Alopecia as the first manifestation of azathioprine myelosuppression in a genetically predisposed patient

Abstract

Azathioprine, an analog of mercaptopurine, is used for various inflammatory/autoimmune diseases in diverse fields such as rheumatology, ophthalmology, gastroenterology, and neurology. One of the dreaded side effects of this drug is myelosuppression, which can be either dose related or “idiosyncratic.” The latter group often manifests with sudden cytopenias and is often secondary to a genetic predisposition. Mutations in the genes thiopurine S-methyltransferase (TPMT) and nucleoside diphosphate-linked moiety X-type motif 15 (NUDT15) have been identified to predispose to severe myelosuppression with azathioprine. An important clinical clue that can precede the onset of myelosuppression is alopecia. Here, we describe the case of a young lady treated with azathioprine, who developed alopecia (progressing to alopecia totalis), which was followed by severe cytopenia – both of which recovered on stopping the drug. On genetic analysis, she was found to be homozygous for mutation in NUDT15 (C415T) but was negative for mutation in TPMT. We review various other cases reporting alopecia as a marker of azathioprine-induced myelosuppression and the genetic mutations described.