Fatal Case of Severe Fever with Thrombocytopenia Syndrome Complicated by Profound Neutropenia and Invasive Trichosporonosis.

Severe fever with thrombocytopenia syndrome (SFTS), a tick-borne viral hemorrhagic fever, is frequently complicated by secondary infections. While invasive aspergillosis is a well-known complication, invasive trichosporonosis has rarely been reported. We describe a fatal case of SFTS complicated by profound neutropenia and subsequent invasive trichosporonosis caused by Cutaneotrichosporon dermatis (formerly Trichosporon dermatis). A 71-year-old woman was clinically diagnosed with hemophagocytic lymphohistiocytosis, for which she received corticosteroids and etoposide. She was transferred to our hospital and diagnosed with SFTS, and favipiravir was immediately initiated. She developed profound neutropenia and subsequently progressed to respiratory failure necessitating mechanical ventilation, for which she was empirically treated with piperacillin/tazobactam and micafungin. Shortly thereafter, progressively elevated serum Aspergillus galactomannan antigen levels raised concern for invasive fungal infection, particularly invasive pulmonary aspergillosis, prompting a switch in antifungal therapy to isavuconazole. However, blood cultures obtained the following day yielded C. dermatis, confirmed by molecular analysis. Despite antifungal treatment and intensive supportive care, the patient died of multiple organ failure. This case highlights the need for close hematologic monitoring and vigilance for invasive fungal infections, including uncommon pathogens such as Trichosporon species, in patients with SFTS.