We report the first two proven cases of cavitary pulmonary zygomycosis caused by Rhizopus homothallicus. The diagnosis in each case was based on histology, culture of the causal agent, and the nucleotide sequence of the D1/D2 region of the 28S ribosomal DNA.
CASE REPORTCase 1 involved a 47-year-old male with a history of type II diabetes mellitus for 13 years who developed diabetic nephropathy leading to end-stage renal disease. He had undergone renal transplantation and was on triple-drug immunosuppression (cyclosporine, azathioprine, and prednisolone). One month posttransplantation, he developed an intermittent fever with chills and pleuritic chest pain. A chest X-ray revealed a cavitary lesion in the right upper lobe with bilateral nodular infiltrates, for which he was treated with a primary drug regimen of antituberculosis therapy (ATT), although multiple sputum examinations were negative for acid-fast bacilli. The patient did not respond to the ATT and was referred to our institute (Postgraduate Institute of Medical Education and Research [PGIMER], Chandigarh, India). At our institute, contrast-enhanced computed tomography (CT) of the thorax revealed a thick, smooth-walled cavitary lesion of the posterior segment of the right upper lobe and multiple nodules in both lungs (Fig. 1). No pleural effusion was noticed. Echocardiography ruled out endocarditis. His blood sugar levels ranged from 153 to 226 mg/dl. While he was at the hospital, he was treated with human insulin therapy. ATT was continued along with vancomycin and tazobactam. Ultrasound-guided fine-needle aspiration of the cavitary lesion of the lung was performed. Direct microscopic examination of calcofluor white-stained mounts of the aspirated fluid was done. Part of the fluid was cultured on Sabouraud dextrose agar (SDA) and brain heart infusion agar (HiMedia, Mumbai, India). Direct microscopy of the aspirated fluid did not reveal any fungal elements, nor did the cultures yield any fungal colonies during 4 weeks of incubation. As the patient did not improve until the 20th day of his hospital stay, an open-lung biopsy was performed. It revealed pus in the pleural cavity with a large cavitary lesion in the right upper lobe. No apparent mass was noticed. A wedge-shaped biopsy sample was taken from the site of the lesion. Tissue slides stained by the hematoxylin-and-eosin and periodic acid-Schiff procedures showed dense acute inflammatory infiltrates across the interstitial septa, a dense fibrosis surrounding the alveoli, extensive necrosis with nuclear debris and broad, aseptate, ribbon-like hyphae (Fig. 2). The causal fungus was observed invading the vessel wall. Culture of the biopsy tissue on SDA (HiMedia, Mumbai, India) grew a fast-growing, floccose white colony turning grayish. Microscopic examination of the colony showed broad, aseptate hyphae with lateral not-well-developed sporangiophores bearing globose sporangia containing a small number of sporangiospores. In addition, a large number of golden brown zygospores with stellate walls and wit...