Cryptococcus Kidney Infection

Cryptococcosis is thought to result from failure of host defenses to contain the organism after inhalation of aerosolized particles from an environmental source. The organism is tropic to the central nervous system (CNS) and the majority of the recognized infections in humans involve meningitis. The disease is not contagious. Most infections in healthy subjects are asymptomatic or mildly symptomatic but self-limited; antifungal therapy is seldom required.

Many reported cases of cryptococcosis ocurre in HIV-positive patients. Current data suggest that 20–60% of the cases of cryptococcosis in HIV-negative patients occurred in organ transplant recipients. Cryptococcosis usually occurs more than 6 months after transplantation.

In H&E-stained tissue sections, C. neoformans appears as eosinophilic or lightly basophilic, uninucleate, thin-walled, spherical, oval, and elliptical yeast-like cells that vary in size from 2 to 20 µm, but commonly measure 4 to 10 µm in diameter. Tipically, the fungal cells are surround by wide, clear to faintly stained spherical zones or "halos" that represent mucinous capsules (Figures 3 to 6). The mucopolysaccharide capsular material is readily demonstrated with mucin stains such as mucicarmin, alcian blue or colloidal iron. This staining reaction is a diagnostic marker, but it may be absent or equivocal if have been digested by phagocytes. This staining reaction is not present in Histoplasma, and it has a more small and less variable size than Cryptococcus (usually 2-5 µm). C. neoformans is the only pathogenic fungus that has a mucinous capsule. On electron microscopy, Cryptococci have electron dense capsules and a well-organized cell wall divided into two layers. The capsules are segmented by radiating, corona-like moderately electron dense fibrillar material. The outer layer of the wall is more electron lucent and the inner wall layer is more electron-dense and it has lamellar configuration (Figures 9 and 10).

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