A69-17 Pulmonary Mucormycosis in a Stable Post-Hematopoietic Stem Cell Transplant Patient: A Diagnostic Challenge

Abstract Introduction Mucormycosis is an opportunistic fungal infection that typically occurs in immunocompromised hosts, particularly in patients with hematologic malignancies, hematopoietic stem cell transplant (HSCT), iron overload, or uncontrolled diabetes mellitus. Recognition of atypical presentations outside the acute transplant window is critical, because delayed diagnosis carries high morbidity and mortality. We present an unusual case of isolated pulmonary mucormycosis in a patient with prior HSCT, no longer on immunosuppression or antifungal prophylaxis. Case Report A 63-year-old male with past medical history of accelerated phase chronic myeloid leukemia status post allogeneic HSCT eight months prior presented with worsening cough and fever. Prior to transplant, there was a persistent right upper lobe cavitary lesion on computed tomography (CT). Multiple prior bronchoscopies with bronchoalveolar lavage (BAL) and CT-guided tissue biopsy were negative for malignancy, AFB, or other notable causes of cavitary lung disease. Infectious prophylaxis after transplant included trimethoprim-sulfamethoxazole, acyclovir, and isavuconazole; however, isavuconazole prophylaxis was completed after day 100 post-transplant and no longer part of his regimen upon presentation. Given continued symptoms and progression of the cavitary lesion (Figure 1) despite antimicrobials, atypical infections and non-infectious causes, such as pulmonary Sweet syndrome, were considered as differential diagnoses. The patient underwent repeat bronchoscopy with BAL and transbronchial biopsy. Pathology revealed broad, aseptate fungal hyphae consistent with mucormycosis, prompting initiation of liposomal Amphotericin B. Thoracic surgery performed a video-assisted thoracoscopic right upper lobectomy with mediastinal lymph node dissection. Pathology from the resected tissue confirmed invasive mucormycosis. Following surgical resection and antifungal initiation, the patient demonstrated clinical improvement and was transitioned to oral isavuconazonium on discharge. Discussion Mucormycosis is a rapidly progressive fungal infection mainly affecting immunocompromised hosts. Pulmonary involvement typically presents with nonspecific symptoms, making early recognition challenging. In our patient, multiple prior nondiagnostic bronchoscopies delayed identification. Definitive diagnosis is usually established through bronchoscopy with histopathologic confirmation via tissue biopsy, as cultures frequently yield false-negative results. Most cases of pulmonary mucormycosis occur in severely immunocompromised patients, but emerging reports describe cases in relatively immunocompetent hosts, potentially related to pulmonary injury or prior broad-spectrum antibiotic use. While most cases are aggressive with high morbidity, our patient had indolent symptoms over several weeks. Early diagnosis, prompt initiation of liposomal amphotericin B, and surgical resection are the mainstays of therapy. This case highlights the importance of increased clinical suspicion for mucormycosis when radiographic and clinical findings remain unexplained, even in patients no longer on immunosuppression or antifungal prophylaxis. This abstract is funded by: None