Cryptococcosis

Cryptococcosis is caused by encapsulated yeast Cryptococcus neoformans (var. grubii, var. neoformans) found worldwide in pigeon excreta and decaying organic matter, and Cryptococcus gattii (Vancouver Island, Pacific Northwest, tropics) found in eucalyptus trees. Infection occurs by inhalation of yeast cells or basidiospores, with primary pulmonary involvement followed by hematogenous dissemination, particularly to the CNS due to neurotropic factors.

Clinical syndromes include cryptococcal meningoencephalitis (most common in advanced HIV with CD4 <100, also in transplant recipients, corticosteroid users), pulmonary cryptococcosis (asymptomatic to lobar pneumonia), cutaneous cryptococcosis (often disseminated marker), and rarely bone, prostate, eye involvement. Cryptococcal meningitis presents subacutely with headache, fever, altered mental status, and elevated opening pressure (>250 mmH2O common, requires LP for relief).

Diagnosis includes serum and CSF cryptococcal antigen (CrAg by latex agglutination or lateral flow assay, highly sensitive and specific), India ink staining of CSF, fungal cultures, and brain MRI (gelatinous pseudocysts, hydrocephalus). Treatment per IDSA guidelines includes induction with liposomal amphotericin B 3-4 mg/kg/day + flucytosine 100 mg/kg/day for 2 weeks, consolidation with fluconazole 800 mg/day for 8 weeks, and maintenance with fluconazole 200 mg/day until CD4 >100 for 1 year (in HIV).