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14 : Zygomycosis
Category: Clinical Microbiology
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There is now accumulating evidence that receipt of prophylaxis or treatment with voriconazole and the severity of the immunosuppression appear to work in conjunction to favor increase in the incidence of zygomycosis in hematopoietic stem cell transplantation (HSCT) recipients. This increase in zygomycosis stands in contrast to prior reports of breakthrough infections seen when fluconazole or itraconazole was used for antifungal prophylaxis in HSCT recipients. The importance of iron availability in the pathogenesis of zygomycosis is underscored by the increased incidence of zygomycosis in patients on deferoxamine therapy or with iron overload. Sinus disease is estimated that about two-thirds of the cases of sinus zygomycosis occur in diabetic patients, often in the presence of diabetic ketoacidosis. Opacification of the paranasal sinuses, fluid levels, bone destruction, and osteomyelitis are the main radiographic findings associated with sinus zygomycosis. Among the different sites, primary pulmonary infection is more frequently associated with disseminated zygomycosis. The presenting signs, symptoms, and radiographic findings of zygomycosis are nonspecific and should be interpreted with respect to the underlying condition of the patient. Despite the recent advances in antifungal therapy, zygomycosis continues to be one of the most fulminant mycoses in humans. Correction of the patient’s underlying condition that predisposes to zygomycosis is one of the cornerstones of successful management of this devastating infection. Surgical debridement is of critical importance for the successful management of zygomycosis. Zygomycetes cause disease in a number of susceptible hosts with different predisposing conditions, including surgery, burns, trauma, diabetes mellitus, and treatment with deferoxamine.
Rhinocerebral zygomycosis, demonstrating left ethmoidal infection, disruption of the lamina papyracea, invasion of the orbital compartment, proptosis of the globe of the eye, sphenoidal sinusitis, cavernous sinus involvement, and a cerebellar pontine infarct.
Pulmonary zygomycosis. The CT image demonstrates early pulmonary zygomycosis involving the left lower lobe, with multiple small nodular infiltrates, including a larger peripheral subpleural nodule surrounded by a delicate alveolar infiltrate.
Histological characteristics of invasive zygomycosis. The isolate of Rhizopus in this excisional biopsy specimen of the kidney demonstrates broad, ribbon-like, sparsely septated hyphae with nondichotomous “right-angled” branching.
Photomicrographs of three medically important genera of Zygomycetes: Rhizopus (top), Mucor (middle), and Cunninghamella (bottom). (Top) The rhizoids, or root-like structures, of the genus Rhizopus arise from the base of the connection between the sporangiophores and stolon. The sporangia in this photomicrograph have opened to release their contents of sporangiospores (original magnification, ×200). (Middle) The genus Mucor is characterized by the absence of rhizoids at the junction between the sporangiophores and stolon. The curved sporangiophores in this photomicrograph are typical of Mucor circinelloides (original magnification, ×400). (Bottom) The sporangium of Cunninghamella is distinct in having sporangioles on the surface of the sporangium (original magnification, ×630). Sporangioles of Cunninghamella spp. are connected to the sporangium by short processes known as ostioles.
Therapeutic approach to zygomycosis.