Cryptococcal meningoencephalitis

Tuberculosis, caused by Mycobacterium tuberculosis, remains a leading global cause of infectious death and presents as latent infection, primary/secondary pulmonary disease, or extrapulmonary and disseminated (miliary) disease. Diagnosis rests on AFB smear, NAAT, and mycobacterial culture (the gold standard), and drug-susceptible active disease is treated with a four-drug regimen (isoniazid, rifampin, pyrazinamide, ethambutol) for 2 months followed by isoniazid plus rifampin for 4 to 7 months.

Acute purulent infection of the meninges beyond the neonatal period, most often from Streptococcus pneumoniae or Neisseria meningitidis, diagnosed by CSF analysis after prompt lumbar puncture and treated with immediate empiric intravenous antibiotics plus adjunctive dexamethasone, since any delay in therapy worsens outcome and mortality remains near 25%.

Herpes simplex virus type 1 or 2 establishes lifelong latency in sensory ganglia after mucocutaneous infection, causing painful vesicular-to-ulcerative outbreaks of the mouth or genitals with intermittent asymptomatic shedding; diagnosis is by NAAT of an ulcer swab and treatment is oral nucleoside analogues, escalating to intravenous acyclovir for encephalitis, severe mucocutaneous disease, or disseminated infection in immunosuppressed hosts.

Toxoplasmosis is infection with the protozoan Toxoplasma gondii, acquired from undercooked meat or cat feces, causing a mononucleosis-like illness in immunocompetent hosts, reactivation encephalitis with ring-enhancing brain lesions in advanced HIV, and a severe congenital syndrome after maternal primary infection in pregnancy. Diagnosis in CNS disease is largely presumptive on serology, imaging, and empiric treatment response, and management is pyrimethamine-sulfadiazine-leucovorin, with prevention centered on CD4-based prophylaxis and food/cat-litter precautions in pregnancy.

Coccidioidomycosis, or valley fever, is a dimorphic fungal infection acquired by inhaling Coccidioides arthroconidia in the southwestern United States, ranging from self-limited pneumonia to disseminated or meningeal disease, diagnosed by culture, histopathology, or serology and treated with fluconazole for symptomatic disease and lifelong fluconazole for meningitis.

Histoplasma capsulatum is an endemic dimorphic fungus, acquired by inhalation of conidia in the Mississippi and Ohio River valleys and other endemic regions, that most often causes asymptomatic or mild pulmonary infection but can disseminate in immunosuppressed hosts; diagnosis rests on the Histoplasma urinary antigen assay and treatment is itraconazole for mild to moderate disease or liposomal amphotericin B followed by itraconazole for severe or disseminated infection.

Acute HIV infection, also called the acute retroviral syndrome, is the symptomatic viremic phase in the days to weeks after HIV acquisition, presenting with fever, fatigue, myalgia, rash, and pharyngitis at a time when antibody testing may still be negative. Diagnosis requires an HIV RNA viral load, and antiretroviral therapy should begin as soon as the patient is ready, regardless of CD4 count.

Brucellosis is a zoonotic infection from unpasteurized dairy, undercooked meat, or animal contact causing undulant fever, hepatosplenomegaly, arthralgia, and depression, diagnosed by extended-incubation blood or marrow culture and serum agglutination titer, and treated with doxycycline plus rifampin or gentamicin for six weeks.

HIV-associated neurocognitive disorders (HAND) span a spectrum from asymptomatic neurocognitive impairment to HIV-associated dementia, caused by chronic HIV infection and inflammation of CNS microglia, and occur regardless of antiretroviral treatment status; diagnosis is one of exclusion after ruling out opportunistic and metabolic causes of cognitive decline, and antiretroviral therapy initiation or optimization is the primary treatment, with efavirenz avoided for its neuropsychiatric effects.