Residency · Residency · Emergency Medicine

HIV-Related Emergencies and Opportunistic Infections

Introduction

Despite advances in antiretroviral therapy (ART), HIV-related emergencies remain a significant component of emergency medicine practice. Patients may present with undiagnosed HIV, known HIV with medication non-adherence, or complications of long-term ART. The CD4 count is the primary determinant of susceptibility to opportunistic infections (OIs), and understanding the relationship between immunosuppression severity and specific pathogens is essential for the emergency physician.

CD4 Count and Opportunistic Infection Risk

The CD4 count serves as the roadmap for predicting which opportunistic infections a patient is susceptible to. When the CD4 count remains above 500 cells per microliter, infections are generally similar to those seen in immunocompetent patients. As the count drops to 200 to 500, patients become vulnerable to oral candidiasis (thrush), multi-dermatomal herpes zoster, bacterial pneumonia, pulmonary tuberculosis, and Kaposi sarcoma. At 100 to 200, the hallmark infection is Pneumocystis jirovecii pneumonia (PJP), along with coccidioidomycosis and histoplasmosis. When the count falls to 50 to 100, cerebral toxoplasmosis, cryptococcal meningitis, and esophageal candidiasis become major concerns. Below 50, the most devastating infections emerge: Mycobacterium avium complex (MAC), CMV retinitis and colitis, primary CNS lymphoma, and progressive multifocal leukoencephalopathy (PML).

Pneumocystis Jirovecii Pneumonia (PJP)

Clinical Features

PJP is the most common opportunistic infection and AIDS-defining illness, occurring when the CD4 count drops below 200 cells per microliter. It has a characteristically subacute onset over days to weeks, presenting with progressive dyspnea, non-productive cough, fever, and malaise. Hypoxia is often more severe than expected from the examination or imaging findings. Exertional desaturation is a characteristic early finding that should prompt suspicion for PJP in the right clinical context.

Diagnosis

The chest X-ray typically shows bilateral interstitial or ground-glass opacities in a perihilar distribution, though it may be normal in early disease, and cysts and pneumothorax can occur. CT of the chest reveals diffuse ground-glass opacities with cystic changes in severe cases. LDH is elevated above 500 IU/L in most cases and is sensitive but not specific. Beta-D-glucan levels above 80 pg/mL serve as a highly sensitive screening test. Definitive diagnosis requires induced sputum with direct fluorescent antibody (DFA) or bronchoalveolar lavage (BAL) with methenamine silver or DFA staining.

Treatment

The drug of choice is TMP-SMX at 15 to 20 mg/kg per day of the TMP component, administered IV or orally for 21 days. Adjunctive corticosteroids are indicated when the PaO2 is below 70 mmHg or the A-a gradient exceeds 35 mmHg, as they reduce mortality by 50 percent. The regimen is prednisone 40 mg orally twice daily for 5 days, then 40 mg daily for 5 days, then 20 mg daily for 11 days. Alternative regimens include IV pentamidine, oral atovaquone, and clindamycin plus primaquine.

<image>Chest X-ray showing bilateral diffuse ground-glass opacities in a perihilar distribution characteristic of Pneumocystis jirovecii pneumonia, with an inset CT image showing the corresponding ground-glass pattern on high-resolution CT</image>

CNS Opportunistic Infections

Cerebral Toxoplasmosis

Cerebral toxoplasmosis is the most common cause of focal brain lesions in AIDS, occurring when the CD4 count falls below 100. It results from reactivation of latent Toxoplasma gondii infection and presents with headache, confusion, fever, focal neurological deficits, and seizures. CT or MRI reveals multiple ring-enhancing lesions with surrounding edema, preferentially located in the basal ganglia. Toxoplasma IgG is positive in 95 percent of cases, and a negative IgG makes the diagnosis unlikely. Treatment consists of pyrimethamine plus sulfadiazine plus leucovorin for a minimum of 6 weeks, and empiric therapy is typically initiated without biopsy. Clinical and radiographic improvement is expected within 10 to 14 days. If no improvement occurs, biopsy should be performed to evaluate for CNS lymphoma.

Cryptococcal Meningitis

Cryptococcal meningitis is caused by Cryptococcus neoformans and occurs with a CD4 count below 100. The onset is insidious, with headache being the most common symptom, accompanied by fever, malaise, and nausea. Nuchal rigidity may be absent. Elevated intracranial pressure is common and represents a major cause of morbidity and mortality. CSF analysis shows lymphocytic pleocytosis (which may be minimal), elevated opening pressure above 25 cm H2O in 70 percent of cases, low glucose, positive India ink stain in 60 to 80 percent, and positive cryptococcal antigen (CrAg) with sensitivity exceeding 95 percent. Serum CrAg serves as a screening test with sensitivity above 99 percent. Treatment involves amphotericin B plus flucytosine for 2 weeks of induction, followed by fluconazole for consolidation and maintenance. Serial therapeutic lumbar punctures are essential for managing elevated intracranial pressure, with the goal of reducing pressure by 50 percent or to below 20 cm H2O.

Progressive Multifocal Leukoencephalopathy (PML)

PML is caused by JC virus reactivation and occurs with a CD4 count below 100. It presents with progressive focal neurological deficits without fever or headache, including hemiparesis, ataxia, visual field cuts, and cognitive decline. MRI shows non-enhancing white matter lesions without mass effect, typically in the parieto-occipital regions. There is no specific antiviral therapy, and treatment relies on immune reconstitution with ART. The prognosis remains poor even with ART initiation.

<image>Comparison of brain MRI images showing ring-enhancing lesions of cerebral toxoplasmosis in the basal ganglia (left panel), a single homogeneously enhancing periventricular lesion of primary CNS lymphoma (center panel), and non-enhancing white matter lesions of PML (right panel), with labeled differentiating features</image>

Gastrointestinal Emergencies

Esophageal candidiasis presents with dysphagia and odynophagia and is diagnosed clinically in HIV patients who have oral thrush and esophageal symptoms. Treatment is fluconazole 200 mg orally daily for 14 to 21 days, with endoscopy reserved for patients who do not respond. CMV colitis occurs with a CD4 count below 50 and presents with bloody diarrhea, abdominal pain, and fever. Diagnosis is made by colonoscopy with biopsy showing intranuclear inclusion bodies, and treatment is IV ganciclovir. MAC presents with chronic diarrhea, wasting, fever, and anemia in patients with a CD4 count below 50. Diagnosis relies on mycobacterial blood cultures or tissue biopsy, and treatment is clarithromycin plus ethambutol.

Immune Reconstitution Inflammatory Syndrome (IRIS)

IRIS is a paradoxical clinical worsening that occurs after ART initiation, caused by the recovering immune system mounting an inflammatory response against previously subclinical opportunistic infections. It typically occurs within 4 to 8 weeks of starting ART, coinciding with a rising CD4 count and falling viral load. The infections most commonly associated with IRIS include TB, MAC, cryptococcal meningitis, PJP, CMV retinitis, and Kaposi sarcoma. Management involves continuing ART (unless the IRIS is life-threatening), treating the underlying opportunistic infection aggressively, and adding corticosteroids for severe cases. Current guidelines favor early ART initiation within 2 weeks for most opportunistic infections, with the notable exceptions of TB meningitis and cryptococcal meningitis, where established infection should be treated first.

Other ED Considerations

HIV-Associated Emergencies

Acute retroviral syndrome is a mononucleosis-like illness occurring 2 to 4 weeks after primary HIV infection, presenting with fever, pharyngitis, rash, lymphadenopathy, and aseptic meningitis. It is frequently missed, and diagnosis requires ordering an HIV RNA viral load because the fourth-generation antigen/antibody test may still be negative at this stage. ART-related toxicity includes lactic acidosis from NRTIs, nephrolithiasis from indinavir, hepatotoxicity from nevirapine, and hypersensitivity reactions from abacavir (associated with HLA-B*5701). Protease inhibitors and NNRTIs have extensive CYP450 interactions, and drug interactions should always be checked before prescribing in the ED.

Post-Exposure Prophylaxis (PEP)

PEP is indicated after high-risk exposures such as needlestick injuries, sexual assault, and unprotected sex with an HIV-positive partner. It should be initiated within 72 hours of exposure, with earlier initiation providing better outcomes. The preferred regimen is tenofovir/emtricitabine (Truvada) plus raltegravir or dolutegravir for 28 days. Baseline laboratories include HIV testing, hepatitis B and C serologies, CBC, creatinine, and liver function tests. Follow-up HIV testing is performed at 4 to 6 weeks and 3 months post-exposure.

<image>Flowchart for emergency department management of suspected opportunistic infections in HIV patients, with decision branches based on CD4 count ranges, primary presenting symptoms (respiratory, neurological, gastrointestinal), and corresponding diagnostic workup and empiric treatment algorithms</image>

Clinical Pearls

The CD4 count is the most important predictor of opportunistic infection risk, and the emergency physician should always attempt to obtain a recent value. PJP should be suspected in any HIV patient with subacute dyspnea and bilateral ground-glass opacities, and adjunctive steroids reduce mortality in severe cases. Multiple ring-enhancing brain lesions in an AIDS patient should be treated empirically for toxoplasmosis, with biopsy reserved for non-responders. Cryptococcal meningitis may present with minimal CSF abnormalities, making it essential to always check CrAg and opening pressure. PEP must be initiated within 72 hours, and the emergency physician should be prepared to prescribe the initial regimen.

References

1. Huang L, Cattamanchi A, Davis JL, et al. HIV-associated Pneumocystis pneumonia. Proc Am Thorac Soc. 2011;8(3):294-300.
2. Panel on Opportunistic Infections in Adults and Adolescents with HIV. Guidelines for the prevention and treatment of opportunistic infections in adults and adolescents with HIV. AIDSinfo. Updated 2023.
3. Perfect JR, Dismukes WE, Dromer F, et al. Clinical practice guidelines for the management of cryptococcal disease: 2010 update by the Infectious Diseases Society of America. Clin Infect Dis. 2010;50(3):291-322.
4. Kuhar DT, Henderson DK, Struble KA, et al. Updated US Public Health Service guidelines for the management of occupational exposures to HIV and recommendations for postexposure prophylaxis. Infect Control Hosp Epidemiol. 2013;34(9):875-892.

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