A Case of Microscopic Polyangiitis Complicated by Mucormycosis: A Dangerous Balancing Act.

Microscopic polyangiitis (MPA) is a rare antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis marked by renal involvement, which often leads to rapidly progressive glomerulonephritis. Immunosuppressive treatment is necessary to prevent irreparable organ damage. On the other hand, mucormycosis is a rare and devastating opportunistic fungal infection with a high mortality rate in both immunosuppressed and immunocompetent individuals. It requires a high index of suspicion at the time of diagnosis since any delay in treatment may lead to severe morbidity or death. Here, we present the case of a diabetic patient diagnosed with MPA who received partial induction treatment, subsequently developed mucormycosis, survived, yet required continued immunosuppressive treatment for active MPA while imaging was concerning for a persistent mucormycosis infection. This case highlights the barriers to early mucormycosis detection specific to vasculitis patients, mucormycosis considerations unique to the rheumatologic population, and discusses how to balance immunosuppressive treatment in the setting of a deadly opportunistic infection.