Opportunistic diseases in HIV infection

Toxoplasmosis: CNS Involvement and Management Tactics

Diagnosing toxoplasmosis in HIV patients is often challenging. The baseline marker is specific IgG, detected in the vast majority of patients. CSF PCR is highly specific but has low sensitivity. Therefore, ex juvantibus therapy (trial treatment) becomes a crucial criterion: if the diagnosis is correct, the lesions on the tomogram significantly decrease within 7–10 days. If there is no response, primary lymphoma, tuberculosis, or brain abscess are ruled out.

Treatment in the acute phase lasts at least 6 weeks and is based on a combination of drugs:

• Pyrimethamine (with a loading dose).
• Sulfadiazine (dosed by body weight).
• Leucovorin (folinic acid) is mandatory to prevent hematological toxicity.

Dexamethasone is prescribed to relieve increasing cerebral edema. If the CD4+ count drops below 100 cells/µL, the patient is indicated for lifelong (until immune status recovery) secondary prophylaxis with the same drugs in reduced doses or co-trimoxazole.

Pneumocystis Pneumonia

The causative agent of pneumocystosis, Pneumocystis jirovecii, is a taxonomic paradox: genetically it is a yeast-like fungus, but morphologically it behaves like a protozoan. In immunocompetent individuals, it causes only transient asymptomatic carriage. However, when CD4+ drops below 200 cells/µL, the infection manifests as severe pneumonia.

Disease development is usually gradual, with progressive dyspnea, dry cough, and fever. In case of an acute onset, rapidly progressive respiratory failure with tachypnea (up to 50 respiratory movements per minute) and acrocyanosis occurs. Without treatment, mortality reaches 100%.

The radiological picture is specific: bilateral diffuse infiltrates spreading from the hila, "ground-glass opacity" and "cotton wool lung" phenomena. Pleural effusion and distinct focal lesions are atypical. Treatment is started immediately, the drug of choice is co-trimoxazole for a course of at least 21 days. In severe hypoxia, the regimen is augmented with glucocorticoids.

Candidiasis against the Background of Immunosuppression

Yeast-like fungi of the genus Candida (most commonly C. albicans) cause stubborn lesions in HIV-infected individuals, the severity of which directly correlates with the level of CD4+ T-lymphocytes.

• Superficial forms (CD4+ level 250–300 cells/µL): mucosal and skin lesions without marked intoxication. Painful plaque-like "cheesy" deposits, severe burning, and persistent vulvovaginitis are characteristic.
• Deep forms (CD4+ level < 100 cells/µL): always proceed with fever. Visceral lesions (candidal esophagitis with odynophagia) and disseminated forms are typical.

Dissemination leads to candidal endophthalmitis with the risk of blindness (fundoscopic examination reveals "fluffy" yellow-white lesions) and CNS involvement in the form of abscesses or meningitis. Diagnosis is based on microscopy and culture methods. Treatment of local forms is carried out with local antimycotics, systemic forms with fluconazole, itraconazole, or intravenous amphotericin B.

Cryptococcosis: Threat to the Nervous System

Cryptococcosis is caused by encapsulated fungi of the genus Cryptococcus, whose reservoir is often bird droppings. The portal of entry for the infection is the lungs. Under conditions of severe immunodeficiency (CD4+ < 100 cells/µL), the process is not limited to lung tissue, but disseminates hematogenously, affecting the meninges.

In 65–85% of cases, the disease occurs in the form of subacute meningoencephalitis. Clinical features include debilitating headache, vomiting, seizures, and hyperesthesia. Classical meningeal signs may be absent in HIV patients. The pulmonary form also proceeds severely, accompanied by acute respiratory failure; chest X-rays often show isolated "coin" infiltrates without signs of calcification.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Clinical interpretation of CSF profiles in candidal and cryptococcal meningeal involvement.
• Features of the differential diagnosis of pulmonary cryptococcosis with neoplasms and miliary tuberculosis.
• Specifics of ENT organ involvement in extrapulmonary pneumocystosis.
• Indications and regimens for pentamidine and dapsone in the prophylaxis of opportunistic pneumonias.

Other topics in the section "Viral Hepatitis and HIV"

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