Deposition of calcium salts in a case of pulmonary zygomycosis: histopathologic and chemical findings

We report a case of pulmonary zygomycosis associated with unusual deposition of calcium salt crystals. The patient was a 75-year-old female who had onset of cough and shortness of breath. She was treated for community-acquired pneumonia but died despite intensive therapy. Postmortem examination revealed diffuse alveolar damage and multifocal necrotizing pneumonia associated with herpes simplex infection and invasive zygomycosis. Birefringent particles were seen associated with fungal elements in the lung parenchyma, within bronchial cartilage, and in blood vessel walls. By infrared spectroscopy, the birefringent particles in the pulmonary parenchyma and within bronchial cartilage had spectral characteristics of calcium oxalate dihydrate and calcium oxalate monohydrate, respectively. The birefringent crystals within vascular walls were identified as calcium carbonate. This case documents the chemical composition and location of 3 different calcium salt crystals in pulmonary zygomycosis. It also shows that among pulmonary fungal infections, calcium oxalate deposition is not restricted to aspergillosis.