FINAL DIAGNOSIS: SEVERE RIGHT LUNG NECROTIZING PNEUMONIA WITH MUCOR
Mucormycosis is a sporadic but cosmopolitan opportunistic infection that occurs in patients with poorly controlled diabetes mellitus, especially when complicated by ketoacidosis - as in this case - as well as in patients with leukemia, or those who receive treatment with corticosteroids or cytotoxic drugs (1). Agents of human mucormycosis include species within the genera Rhizopus, Absidia, Mucor, Rhizomucor, Apophysomyces, Cunninghamella, and Saksenaea. These saprophytic fungi are widely distributed in nature, where they subsist on decaying vegetation and diverse organic materials such as soil, spoiled foods, bread and dust (1). They are normally identified as saprophytic organisms on the mucosal surfaces of the nasal cavity and paranasal sinuses. They show minimal intrinsic pathogenicity toward the normal host, although isolated cases of pulmonary mucormycosis in apparently normal hosts have been reported (2,3).
The hyphae of the mucor species have a characteristic appearance in tissue sections: they are broad, 6 to 25 micrometers wide, thin-walled and pleomorphic, with irregular, nonparallel contours. The branches arise haphazardly, often at right angles to the parent hyphae. Some hyphae contain septa, but most of them appear nonseptate (cenocytic). The hyphae have little structural stability, so they are often folded, twisted, wrinkled, or collapsed. The thin hyphal walls stain with hematoxylin but are best seen on silver stained sections.
The invasive opportunistic infections caused by mucor are characterized by tissue infarction and acute suppurative inflammation. Infarcts are caused by thrombosis complicating hyphal invasion of arteries and veins. Microscopically the lesions are characterized by coagulative necrosis and neutrophilic infiltrates.
Several clinical forms of mucormycosis are recognized (1), such as rhinocerebral mucormycosis, invasive pulmonary mucormycosis, gastrointestinal mucormycosis, cutaneous mucormycosis and disseminated forms, involving almost any organ, such as lungs, central nervous system, spleen, kidneys, heart and gastrointestinal tract. Generally rhinocerebral mucormycosis is seen in diabetic ketoacidosis, whereas the pulmonary and disseminated forms are more often encountered in patients with leukemia and lymphoma.
Invasive pulmonary mucormycosis is a progressive infection characterized by vascular invasion, parenchymal infarction and hematogenous dissemination (4). An endobronchial form which causes bronchial obstruction is described in diabetics (5, 6); this form may lead to serious hemorrhage after hyphal invasion into adjacent blood vessels (7, 8). Early surgical intervention is indicated in these cases, in addition to medical treatment with antifungal agents, because the hemorrhage is often fatal. However, the prognosis for these cases is poor (4).
The patient presented had poorly controlled diabetes mellitus. He developed pulmonary mucormycosis with extensive necrosis of the right lung and bronchial involvement during an episode of diabetic ketoacidosis. He failed to respond to medical treatment and died after an episode of hemoptysis.
Contributed by Octavia Graur, MD, PhD and Robert E Lee, MD