Clinical History:

A 31-year-old woman was diagnosed with HIV infection 6 years ago but was relatively healthy until a year ago, when she developed oral thrush. A month later she was hospitalized for a respiratory tract infection. Streptococcus pneumoniae was cultured. Her most recent hospitalization followed the onset of a fever to 38 C. She also had a cough productive of sputum that was thick and yellow-tinged. A chest radiograph showed patchy areas of consolidation in both lungs.

Answers:

1. What are the possible causes for these findings?

These findings are most typical for a bacterial pneumonia. Cytomegalovirus (CMV) can sometimes produce a florid pneumonitis, and Pneumocystis carinii (jirovecii) pneumonia (PCP) can also produce widespread pneumonia, but a productive cough is unlikely with either CMV or PCP. Fungal pneumonias are not common, though cryptococcal pneumonia can be widespread. A mycobacterial pneumonia is possible but less likely. Remember that there can be more than one organism present simultaneously in immunocompromised patients.

2. What laboratory testing or diagnostic procedures can be performed to reach a diagnosis?

In this case, a previous sputum culture grew S. pneumoniae. This is again the cause for the pneumonia, or an organism such as Staphylococcus aureus, Pseudomonas aeruginosa, or Hemophilus influenzae could be found in sputum. Sputum could also be sent for mycobacterial and fungal culture. CMV can be detected by direct fluorescence antigen testing and culture. If a bronchoalveolar lavage (BAL) is done, the cytologic specimen can be stained with methenamine silver, PAS, and acid fast stains to look for organisms.