Case Presentation: An 80 year old man with pauci-immune glomerulonephritis for one year presented with fatigue and dyspnea. He had been treated with cyclophosphamide and corticosteroids in the last year; at presentation he was taking prednisone, mycophenolate, and rituximab for the past three months. He denied cough, hemoptysis, chest pain, fevers, chills, and weight loss. He had diabetes with a Hemoglobin-A1c of 9.1. He had no recent travel, sick contacts, or smoking history. He had a history of latent tuberculosis and had completed a nine month course of isoniazid. 

The patient had a temperature 100.7 F but otherwise normal vital signs. Examination was unremarkable except for chronic lower extremity edema. Initial labs showed WBC 12.8 with 68% neutrophils. Chest radiography showed a new right upper lobe cavitary lesion. Computed tomography of the chest demonstrated a 4cm cavity with a thickened rind and ground glass halo concerning for tuberculosis. Bronchoscopy demonstrated unremarkable airways without purulence or blood. Bronchoalveolar lavage cultures and acid fast stain were negative; however, serological tests for aspergillus antibodies returned positive. Aspergillus was presumed to be the cause of the lung cavity. The patient was discharged home on oral voriconazole.

He returned two weeks later with dry cough and worsening dyspnea. Repeat computed tomography of the chest revealed an enlarged 6cm cavity with extension into the right lower lobe and ground glass opacities in the right upper and right lower lobes. Repeat bronchoscopy with lung biopsy demonstrated fibrinous mucous material from these regions. Samples were positive for fungal elements on hematoxylin and eosin stain morphologically consistent with mucormycosis. The patient was switched to liposomal amphotericin b and caspafungin. The patient underwent right thoracotomy, right upper lobectomy, and right lower lobe segmental resection. Although the patient developed post-operation pneumonia requiring brief intubation and a seven day course of antibiotics, he recovered well and was transitioned to a month of oral posoconazole.

Discussion: Pulmonary mucormycosis is an uncommon but life-threatening illness affecting immunocompromised individuals, particularly those with diabetes mellitus and hematological malignancies. Diagnosis is difficult but bronchoalveolar lavage and biopsy can be helpful. Radiographically it can present as lobar consolidation, isolated masses, nodular disease, or cavitation. An important finding is extension across tissue planes. Treatment includes antifungal therapy and extensive surgical debridement, though mortality remains >80%.

Conclusions: In summary, we described a case of pulmonary mucormycosis in a patient on immunosuppressive therapy for glomerulonephritis. Interestingly, initial bronchioalveolar lavage did not reveal the diagnosis. However, the patient re-presented with rapid incenlargement in his pulmonary cavity and subsequent repeat bronchoscopy revealed the correct diagnosis, leading to successful combined medical and surgical therapy. Ultimately, this case demonstrates the need to consider pulmonary mucormycosis in immunocompromised patients with cavitary lung disease who lack a definitive microbiological diagnosis.