Mucocutaneous Ulcerations Due to Methotrexate Toxicity Mimicking Vesiculobullous Disorder: A Diagnostic Challenge

Introduction: Methotrexate is an antifolate agent commonly used in various dermatological and rheumatological diseases such as psoriasis, systemic lupus erythematosus, and other connective tissue disorders. Acute toxicity manifesting as mucocutaneous ulcerations is a rare event in 3 - 10% of patients. Normal dosing commonly used for dermatologic and rheumatologic diseases is 15 - 25 mg/week. The main culprit leading to toxicity is the overdose of medication. Nausea, leukopenia, infections, gastrointestinal bleeding, renal impairment, etc. are the common manifestations of methotrexate toxicity. Mucocutaneous ulcerations, though infrequent, can appear as early as 3 - 7 days following methotrexate administration. Thus, it can be the imminent sign of methotrexate toxicity, providing a clue to its timely diagnosis. The crucial steps in the management of methotrexate toxicity are withdrawal of medication, immediate administration of leucovorin which is the biologically active form of folic acid, adequate hydration for increasing renal clearance, and urinary alkalinization with sodium bicarbonate, wherever necessary. Case Presentation: Here, we report an accidental methotrexate overdose in a patient with psoriasis, presenting with extensive mucocutaneous ulceration mimicking autoimmune vesiculobullous disorder and Stevens-Johnson syndrome- toxic epidermal necrolysis, leading to an extremely rare and challenging scenario. Conclusions: This case report emphasizes that careful history and evaluation of medical records facilitate early diagnosis and prompt management, which is critical to improving outcomes and patient’s survival.