Acute Necrotizing Fasciitis Caused by Rhizopus Infection in a Patient with Diabetes and Pulmonary Tuberculosis: A Case Report

Abstract

Background: Zygomycosis, also termed mucormycosis, is a rare yet highly fatal fungal infection caused by Mucorales species, notably Rhizopus spp.

Case presentation: This case study details a 72-year-old man with diabetes, pulmonary tuberculosis, and nephrotic syndrome who developed acute necrotizing fasciitis attributable to R. oryzae. Despite initial empirical antibiotic therapy, the infection progressed rapidly. Metagenomic next-generation sequencing (mNGS) facilitated a swift diagnosis, identifying R. oryzae in blood and drainage samples. The treatment included amphotericin B and isavuconazole, along with aggressive surgical debridement. The patient exhibited substantial improvement, and he was discharged after stabilization.

Conclusion: This case highlights the critical role of early diagnosis through mNGS and the need for a multidisciplinary approach to manage severe mucormycosis in immunocompromised patients.

Keywords: Rhizopus infection; acute necrotizing fasciitis; case report; diabetes.

Figure 1

Fat-saturated T2-weighted magnetic resonance images. (A) Coronal view, (B) axial view, and (C) sagittal view.

Figure 2

Intraoperative findings. (A) Extensive necrosis and exudation of the skin in the upper and middle segments of the left lower leg. (B) Post-excision, superficial venous thrombosis and necrotizing fasciitis with extensive muscle necrosis were observed, and they were most pronounced in the anterior tibial compartment. (C) Following thorough debridement, bleeding was controlled, and the wound was covered with a vacuum sealing drainage dressing for continuous drainage.

Figure 3

Culture and pathological findings. (A and B) Culture: exudates cultured on Sabouraud dextrose agar and potato dextrose agar at 26–28°C for 3 days, revealing colonies that transitioned from white or gray to gray or brown with a dense, fluffy, cotton-like appearance. (C) Smear: rhizoids (beneath the mycelium), smooth hyphae (few or no septa), upright sporangia with spherical, smooth-walled sporangiospores. (D) Pathological findings: extensive necrosis and abundant fungal hyphae in tissue with positivity on periodic acid-Schiff and periodic acid-methenamine silver staining, indicating Rhizopus spp.

Figure 4

Observations before debridement and vacuum sealing drainage (June 19 and 24). (A) On June 19, previously intact skin and muscle deteriorated with expanded necrosis and complete loss of the anterior tibial muscles. (B) By June 24, necrosis had progressed to the knee with severe involvement of the anterior tibial muscles.

Figure 5

Hospital discharge (July 2). Prior to discharge, the vacuum sealing drainage was removed, revealing well-formed granulation tissue and no evidence of further necrotic progression.

Figure 6

Timeline of the patient’s course prior to and during hospitalization.