Case 19 – A 27-year-old woman with fever and cough

A 27-year-old woman presents to her physician because of 5 days of fever and cough. She has no significant past medical history but has been “fighting colds” for the past 3 months, which she attributed to the winter season. She began having low-grade fevers as well as a dry cough 5 days ago. She has also become increasingly short of breath over the past 2 days. Her temperature is 38.7°C (102°F), heart rate is 110/min, respiratory rate is 24/min, blood pressure is 110/70 mm Hg, and oxygen saturation is 90% on room air. Physical examination reveals pallor and oral thrush. Lung auscultation is significant for bilateral crackles and rhonchi throughout. The remainder of her examination is unremarkable. She lives with her husband, who is HIV-positive but is currently asymptomatic. She has no pets and no recent travel history. X-ray of the chest reveals diffuse bilateral interstitial infiltrates.

What is the most likely diagnosis?

The patient’s respiratory symptoms, oral thrush, and radiographic findings are most concerning for Pneumocystis carinii pneumonia (PCP) (now called Pneumocystis jiroveci). PCP is an important cause of pneumonia in immunocompromised hosts and is a leading cause of opportunistic infection, morbidity, and mortality in patients with HIV. The fact that this patient’s husband is HIV positive makes her chance of also being HIV positive very likely.

What is the next step in diagnosis?

Specific diagnosis of PCP requires documentation of the organism in respiratory specimens. Conventional stains such as toluidine blue O, methenamine silver, or Giemsa can be used to identify the organism. Immunofluorescent staining is the most common technique currently in use.

What is the most appropriate management for this patient?

Trimethoprim-sulfamethoxazole (TMP-SMX), which acts by inhibiting folic acid synthesis, is considered the drug of choice for all forms of pneumocystosis. Therapy is continued for 14 days in non-HIV-infected patients and for 21 days in persons infected with HIV. In patients with severe PCP, corticosteroids given in conjunction with anti-Pneumocystis therapy, decreases the incidence of mortality and respiratory failure.

What findings would one expect to see on high-resolution computed tomography (HRCT)?

A patchy or nodular ground-glass appearance is the most common finding of PCP on HRCT. HRCT has a high sensitivity for PCP among HIV-positive patients.

What prophylactic therapy should this patient use for her condition?

Indications for prophylaxis of PCP in HIV-positive patients include:

1. History of PCP
2. CD4 cell count <200/mm³
3. History of oropharyngeal candidiasis

Oral trimethoprim-sulfamethoxazole (TMP-SMX) is the preferred prophylactic regimen. Other options include pentamidine, dapsone, and atovaquone. Oral TMP-SMX is also useful in preventing toxoplasmosis and bacterial infections.

By Jessica Kagen Hart, Resident, Department of General Pediatrics, Children’s Hospital of Philadelphia; in association with Le TT, Schabelman E, Shivaram A, and Klein J, eds: First Aid Cases for the USMLE Step 2 CK. New York: McGraw-Hill, 2007.