Severe Fever with Thrombocytopenia Syndrome Complicated by Mixed Pulmonary Aspergillus and Mucorales Infection and Isavuconazole-Associated Liver Injury: A Case Report

Abstract

Background Severe fever with thrombocytopenia syndrome (SFTS) is a tick-borne viral disease characterized by severe immune dysregulation and high mortality, predisposing patients to opportunistic infections. Case Presentation We report a 76-year-old male patient diagnosed with SFTS complicated by chronic hepatitis B with low-level viral replication, liver injury, and myocardial injury. After initial treatment with intravenous immunoglobulin, hepatoprotective therapy, and antiviral therapy, the patient stabilized. During hospitalization, he developed pulmonary infection. Sputum culture was positive for Aspergillus fumigatus and serum galactomannan (GM) test was positive. Initial treatment with voriconazole led to radiological improvement in the right lung lesion; however, progression of the left lung lesion was observed. Bronchoalveolar lavage fluid metagenomic next-generation sequencing (mNGS) identified Rhizopus microsporus, leading to the diagnosis of invasive pulmonary Aspergillus–Mucorales coinfection. Oral isavuconazole combined with nebulized amphotericin B was administered, resulting in significant clinical and radiological improvement. Approximately one month after isavuconazole therapy, the patient developed jaundice and coagulation dysfunction. After exclusion of hepatitis B virus reactivation and other potential causes, isavuconazole-associated drug-induced liver injury was considered probable based on the clinical course and a RUCAM score of 8. Conclusion SFTS patients are highly susceptible to invasive fungal infections due to immune dysregulation, thrombocytopenia, and endothelial injury. Clinicians should consider mucormycosis in patients with poor response to voriconazole and progressive pulmonary lesions, and early bronchoscopy with mNGS is recommended. Although isavuconazole is considered relatively safe, liver function monitoring is essential, especially in patients with underlying liver disease.