Introduction And Epidemiology

Opportunistic infections represent the primary cause of morbidity and mortality in human immunodeficiency virus-infected children lacking combination antiretroviral therapy.
Infection risk strictly correlates with the degree of immunosuppression, measured by CD4 T-lymphocyte counts and percentages.
Infants under one year face the highest risk and mortality from acquired immunodeficiency syndrome-defining infections, necessitating prompt age-specific prophylaxis regardless of CD4 counts.

Fungal Infections

Constitutes the most common serious opportunistic infection in infants, classically peaking between 3 and 6 months of age.
Clinical Features: Presents insidiously with tachypnea, feeding difficulties, nonproductive cough, and severe hypoxemia out of proportion to auscultatory findings.
Diagnostic Findings: Chest radiography classically reveals bilateral, symmetric ground-glass interstitial infiltrates. Definitive diagnosis requires organism demonstration via bronchoalveolar lavage.
Management Protocol: Intravenous Trimethoprim-Sulfamethoxazole administered for 21 days. Adjunctive corticosteroids are strictly mandatory for moderate to severe disease to prevent inflammatory deterioration.

Infection Type	Clinical Presentation	Management Guidelines
Oropharyngeal Candidiasis	Curd-like white plaques on erythematous mucosa. Persistence beyond 6 months of age strongly suggests disease progression.	Topical Nystatin or Clotrimazole; oral Fluconazole reserved for refractory cases.
Esophageal Candidiasis	Acquired immunodeficiency syndrome-defining illness causing severe dysphagia, odynophagia, and retrosternal pain.	Systemic Fluconazole or Itraconazole administered for 14 to 21 days.
Cryptococcosis	Typically presents as subacute meningitis with fever, headache, and elevated intracranial pressure in severely depleted adolescents.	Induction therapy utilizing Amphotericin B and Flucytosine, followed by Fluconazole consolidation.

Exhibits a synergistic bidirectional interaction with the human immunodeficiency virus; human immunodeficiency virus accelerates tuberculosis progression, while tuberculosis drives human immunodeficiency virus replication.
Clinical Features: Presents with unremitting cough, prolonged fever, weight loss, and intrathoracic lymphadenopathy. Extrapulmonary and disseminated tuberculosis forms are significantly more frequent.
Management: Requires standard four-drug therapy. Rifampicin acts as a potent CYP450 inducer, necessitating critical dose adjustments for concurrent antiretroviral therapy, such as doubling Dolutegravir doses.

Exclusively affects children experiencing severe immunosuppression, defined by a CD4 count below 50 to 75 cells/µL.
Clinical Features: Disseminated disease driving chronic diarrhea, severe anemia, persistent fever, weight loss, and generalized lymphadenopathy.
Management: Combination therapy utilizing Clarithromycin or Azithromycin alongside Ethambutol.

Viral Pathogen	Cardinal Clinical Manifestations	Specific Pharmacotherapy
Cytomegalovirus	Disseminated disease features retinitis demonstrating classic pizza pie retinopathy, severe colitis, and encephalitis.	Intravenous Ganciclovir or Foscarnet.
Herpes Simplex Virus	Chronic ulcerative mucocutaneous lesions persisting beyond 1 month, recurrent severe gingivostomatitis, and disseminated visceral infection.	Acyclovir; Foscarnet strictly utilized for Acyclovir-resistant strains.
Epstein-Barr Virus	Drives Lymphoid Interstitial Pneumonitis characterized by slowly progressive hypoxia and bilateral reticulonodular infiltrates.	Corticosteroids indicated specifically for significant hypoxemia.
JC Virus	Causes Progressive Multifocal Leukoencephalopathy resulting in progressive focal neurologic deficits, cognitive decline, and seizures.	Relies strictly on immune reconstitution via antiretroviral therapy.

Cryptosporidiosis: Causes severe, chronic, cholera-like watery diarrhea and biliary tract disease in profoundly immunosuppressed hosts.
Toxoplasmosis: Central nervous system reactivation causes severe encephalitis presenting with focal signs, seizures, and ring-enhancing lesions on neuroimaging.
Recurrent Bacterial Infections: Profound B-cell dysfunction predisposes children to recurrent bacteremia, meningitis, and pneumonia driven by encapsulated bacteria like Streptococcus pneumoniae and Haemophilus influenzae.

Defined as a paradoxical clinical worsening of pre-existing infectious symptoms or the sudden unmasking of subclinical infections following the initiation of antiretroviral therapy, driven by rapid immune recovery.
Common triggering pathogens include tuberculosis, Mycobacterium avium Complex, and Cytomegalovirus.
Management strictly requires continuing antiretroviral therapy, treating the underlying opportunistic infection, and administering corticosteroids for severe, life-threatening inflammation.

Prophylaxis Target	Medication Protocol	Clinical Indication
Pneumocystis jirovecii	Trimethoprim-Sulfamethoxazole	Mandatory for all exposed infants starting at 4 to 6 weeks of age; continued based on age-specific CD4 thresholds.
Tuberculosis	Isoniazid Preventive Therapy	Administered for 6 months to all infected children older than 12 months lacking active disease.
Mycobacterium avium Complex	Azithromycin or Clarithromycin	Indicated strictly for severe CD4 depletion.
Immunization	Inactivated Vaccines	Universally recommended. Live vaccines like Bacille Calmette-Guérin and Oral Polio Vaccine remain strictly contraindicated in symptomatic infected infants.