Risk of herpes zoster infection in patients with pemphigus on mycophenolate mofetil

Conflicts of interest: none declared. Sir, The use of mycophenolate mofetil (MMF) (CellCept®, Roche, Welwyn Garden City, Herts, U.K.) in dermatology is expanding, particularly in immune‐mediated skin disease. Dermatological indications have included psoriasis and a number of autoimmune bullous skin diseases including pemphigus vulgaris. MMF is typically used at a dose of 2–3 g daily, often together with oral steroid therapy. MMF is an ester of mycophenolic acid (MPA), its active metabolite, which acts by inhibiting inosine monophosphate dehydrogenase in the de novo purine synthesis pathway resulting in impaired RNA, DNA and protein synthesis. Lymphocytes depend primarily on this pathway and thus MMF has significant specificity for this cell type,1 inhibiting proliferation of both T and B lymphocytes. Because of this specificity, MMF is generally well tolerated and the most common dose‐related side‐effects are gastrointestinal and genitourinary in origin. As with any immunosuppressive therapy opportunistic infection is a risk and in organ transplant recipients on MMF and combination immunosuppressants, opportunistic infection has a reported incidence of approximately 40%. In addition to common bacterial and viral infections, patients on MMF are at risk of herpes simplex, cytomegalovirus, candidiasis, cryptococcosis, aspergillosis and Pneumocystis carinii pneumonia.2