Breakthrough mucormycosis after hematopoietic stem cell transplantation: a retrospective multiyear cohort study in Eastern China

BACKGROUND: This study aimed to update the epidemiology and clinical characteristics of mucormycosis, a rare but life-threatening invasive fungal infection in hematopoietic stem cell transplantation (HSCT) recipients. METHODS: We conducted a retrospective, single-center observational study including all consecutive HSCT recipients from November 2020 to October 2024, with follow-up through May 2025. RESULTS: Among 1224 HSCT recipients receiving antifungal prophylaxis, mucormycosis was diagnosed in 49 patients (4.0%), with an incidence density of 3.4 per 100 person-years. The median time to onset was 73.0 days post-transplant (interquartile range, 30.0-223.0 days). Pulmonary involvement was present in 75.5% of cases. Rhizopus spp. accounted for the highest proportion (37.3%) among the isolated fungal genera. Multivariate analysis identified myelodysplastic syndrome (adjusted hazard ratio [aHR] = 2.65), prior fungal infection (aHR = 2.33), and severe acute graft-versus-host disease (aGvHD) (aHR = 2.96) as independent risk factors. Among 43 patients treated with antifungals, the 84-day survival rate was 46.5%. Severe aGvHD was an independent predictor of mortality. Combination therapy with amphotericin B plus posaconazole or isavuconazole was associated with a lower rate of treatment failure compared to amphotericin B alone, although this difference was not statistically significant (42.3% vs. 80.0%; P = 0.172). CONCLUSIONS: Mucormycosis poses a serious risk post-HSCT; early identification and optimized treatment are critical to improving outcomes.