HIV AND AIDS   77A

A 31-year-old man who is an injection drug user presents to the emergency department with a chief complaint of shortness of breath. He describes a 1-month history of intermittent fevers and night sweats associated with a nonproductive cough. He has become progressively more short of breath and now he feels dyspneic at rest. He appears to be in moderate respiratory distress. His vital signs are abnormal, with fever to 39°C, heart rate of 112 beats/min, respiratory rate of 20 breaths/min, and oxygen saturation of 88% on room air. Physical examination is otherwise unremarkable. Notably, the lung examination is normal. Chest radiography reveals a diffuse interstitial infiltrate in a “bat’s wing” or “butterfly” pattern.

What are the salient features of this patient’s problem? How do you think through his problem?

Salient features: Injection drug use; 1-month duration of intermittent fevers and night sweats; pneumonia symptoms (slowly progressive dyspnea, fever, tachycardia, hypoxia); abnormal chest radiograph findings suggesting an opportunistic infection.

How to think through: What are the broad categories in the differential diagnosis for this presentation? (One month of fevers, night sweats, cough, dyspnea, and hypoxia.) Among infections, what are possible causes? Could this be a typical bacterial pneumonia? (Unlikely, given the duration.) How about tuberculosis or a fungal infection (e.g., coccidioidomycosis)? What elements of the case strongly suggest pneumocystis? (The radiography pattern; hypoxia despite normal lung sounds.) At what CD4+ T cell count does pneumocystis become more likely? (<200 cells/mcL.) How is the diagnosis of pneumocystis definitively made? (Sputum induction or bronchoscopy.) What percent of HIV-positive patients in the United States are unaware of their diagnosis? (25%.) When unusual infections enter the differential diagnosis, one must think of HIV even in the absence of known risk factors. Which test is used to diagnose HIV and which to confirm the diagnosis? When, after exposure, is HIV antibody detectable? At what CD4+ T cell count is the diagnosis of AIDS made? (<200/mcL). If this patient’s CD4 count is 50 cells/mcL, what other infectious and noninfectious complications might he develop?

HIV AND AIDS   77B

What are essentials of diagnosis and general considerations regarding HIV?

Essentials of Diagnosis

Risk factors: sexual contact, needle sharing, transfusion, or perinatal exposure

Prominent systemic complaints such as sweats, diarrhea, weight loss, and wasting

Opportunistic infections caused by diminished cellular immunity

Aggressive cancers, particularly Kaposi sarcoma and extranodal lymphoma

Neurologic manifestations, including dementia, neuropathy, and aseptic meningitis

General Considerations

Etiology: HIV-1, a retrovirus

Diagnosis of AIDS generally requires evidence of HIV infection plus the presence of an “AIDS-defining” opportunistic infection or a CD4 count <200 cells/mcL

HIV AND AIDS   77C

What are the symptoms and signs of HIV?

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