Skinternal Medicine: An Update On Cutaneous Manifestations of Systemic Disease (Case 5)

Frank Wang, an associate professor at the University of Michigan, presented a case involving an 82-year-old female with painful oral lesions and a groin rash, complicating her ongoing treatment for seronegative inflammatory arthritis. After a detailed examination, including photos showcasing the erosions of her lips and groin lesions, the discussion highlighted potential diagnoses such as immunobullous disorders and medication toxicity. Ultimately, the case revealed a methotrexate-induced toxicity, due to an inadvertent daily dosing of methotrexate instead of the prescribed weekly dosage. The patient also experienced a sinus infection and was prescribed amoxicillin, contributing to her symptoms. Laboratory tests noted low hemoglobin and elevated BUN, but methotrexate levels were undetectable. The initial treatment involved stopping methotrexate and administering IV leukovorin to manage the mucositis. Wang emphasized the seriousness of methotrexate toxicity, which can manifest as mucosal erosions similar to pemphigus vulgaris and can affect renal function. He outlined risk factors including older age, inadvertent daily dosing, and concurrent medications that may affect methotrexate metabolism. Recommendations concluded with the need for vigilance in monitoring patients on methotrexate, even at low doses, and the importance of recognizing symptoms of toxicity to ensure timely and appropriate management.