Mycoses

C. neoformans : ubiquitous in soil, bird excrement, compost

C. gattii : tropical/subtropical climates, North American western coast

• Eucalyptus trees primarily

• Primarily infects nonimmunocompromised persons

Most common CNS fungal infection in immunocompromised (primarily C. neoformans )

• Increased incidence: alcoholism, sarcoidosis, corticosteroids, immunosuppression/autoimmune

First manifestation of AIDS in up to 70% of HIV-positive adults, rare in children

• Two to seven per 1000 HIV-positive patients affected per year in the United States

Inhaled spores

• Most people clear infection

• Delayed hypersensitivity reaction (positive skin test)

Pulmonary

• Infiltrates, lymphadenopathy, effusions, cavitations

Hematogenous dissemination from lungs (most common route)

• CNS, skin, myocardium, eyes (almost any organ)

• Meningitis (tends to be basal)/encephalitis

• Cryptococcoma: commonly seen in immunocompetent (usually C. gattii )

Subtle onset: relapsing/remitting with vague symptoms

• Headache, fever, generalized discomfort, nausea and vomitting, meningismus, mental status changes, visual complaints

• Seizures, focal neurologic deficits less commonly

Cerebrospinal fluid

• CSF polymerase chain reaction (PCR) for diagnosis

• Protein: normal to 500 mg/dL

• Glucose: normal/mildly decreased

• Pleocytosis (predominantly mononuclear)

Neurotropic: CSF is an excellent growth medium

Mortality rate: 6% to 14% (with treatment)

High relapse rates

Amphotericin B and flucytosine

Opaque/fibrotic meninges (especially base of brain/cerebellum) in nonimmunocompromised patients

Gelatinous-appearing cysts in the basal ganglia

Isolated cryptococcal abscess (cryptococcoma)

Encapsulated ovoid budding yeast (3 to 20 µm)

• Capsule: clear halo on H&E

• Sometimes confused with corpora amylacea

Meningitis with granulomatous inflammation (nonimmunocompromised)

• Spherical organisms with capsule found in subarachnoid space

• Can lead to hydrocephalus/cerebral edema

• Immunocompromised patients: minimal inflammation/necrosis until late stage of the disease

Intraparenchymal lesions

• Cystic “soap bubbles”/solid nodules

• Basal ganglia most common location

• Perivascular “tubercles”: 3 mm or smaller

Cryptococcomas (“Torulomas”)

• Immunocompetent hosts usually

• Mass lesions, sometimes granulomatous

• May involve meninges, ependyma, choroid plexus, parenchyma

Mucicarmine, Gomori methenamine silver (GMS), Alcian blue

Other mass lesions

• Toxoplasmosis, lymphoma, neoplasm

Intracranial hemorrhage

Sarcoidosis

Meningitis/encephalitis/abscess (e.g., bacterial/mycobacterial/parasitic/candida)

Other HIV encephalitides