Abstract

Multisystem Inflammatory Syndrome in Adults (MIS-A) can develop following COVID-19 infection with multiorgan involvement, including the heart, gastrointestinal tract, skin, and brain. Cutaneous manifestations of MIS-A present with highly variable morphologies. Herein, we describe a case of a 50-year-old female presenting with fever, hypotension, weakness, abdominal pain, and pruritic and painful rash following COVID-19 infection. The rash was initially on her face, chest, and abdomen but then progressed to her arms and back. The rash consisted of erythematous to hyperpigmented macules and patches. She had markedly elevated serum inflammatory markers. Clinical differential diagnoses included MIS-A, adult-onset Still's disease, autoimmune disease, infection, or a drug eruption. A punch biopsy was obtained and showed mixed perivascular and interface dermatitis with necrotic keratinocytes in the epidermis and stratum corneum, minimal spongiosis, and patchy parakeratosis. There was focal vacuolar degeneration of basal keratinocytes. The superficial perivascular infiltrate was composed of lymphocytes, plasma cells, neutrophils, and scattered eosinophils. No fibrinoid necrosis of vessels or intraluminal thrombi were identified. Immunofluorescence studies were negative for IgG, IgA, IgM, and C3 staining. The histologic findings were non-specific in this case, however, clinical findings were most consistent with MIS-A following extensive clinical and laboratory investigation for other etiologies. The patient improved following IVIG therapy. This case demonstrates the challenges in diagnosing MIS-A, as histologic findings can appear similar to adult-onset Still's disease and other diagnoses. Correlation with patient presentation is crucial to suspect this rare disease.