List the potential causes of diffuse pulmonary infiltrates in a patient with AIDS, and outline how they would influence your management.
Many potential causes should be considered. High pressure pulmonary oedema (fluid overload: CPAP/PEEP, diurese, fluid restrict, remove blood; cardiac failure: diurese, vasodilate ± inotropes; acute ischaemia: nitrates, morphine ± betablockers, anticaogulants). Low pressure pulmonary oedema/ARDS (CPAP/PEEP, fluid restrict, diurese, treat underlyimg cause eg. sepsis). Diffuse pneumonia (diffuse typical or atypical: CPAP/PEEP, likely to need invasive investigation [eg. lavage], diurese and fluid restrict, specific treatment [anti-agent therapy] according to underlying cause: bacteria [eg. strep or TB], viral [eg. CMV/influenza/SARS], protozoal [eg. pneumocystis], fungal [eg. cryptococcus]). Others: could uncommonly also be malignant (eg. Karposi’s sarcoma), pulmonary haemorrhage (eg. if low platelets: consider platelet transfusion) or auto- immune/vasculitic (consider steroids, immunosuppression).
A good free full-text article is available to cover this terrain. In it, there is an excellent table, "Aetiology of pulmonary infections in HIV-infected patients". It also presents the incidence of the aetiology. Turns out, in 97% of cases the pulmonary infiltrates are infectious in nature. The bacterial pathogens are surprisingly mundane- its S.pneumoniae, H.influenzae and Legionella. Together they cover something like 60% of pulmonary infections. Pneumocystis accounts for another 20%, and viruses for 5%. Other fungal infections are surprisingly rare - 2% - and protozoal parasites represent only 0.5%.
Causes of diffuse pulmonary infiltrates in the AIDS patient, and a brief note on their specific treatment
Segal, Leopoldo N., et al. "HIV-1 and bacterial pneumonia in the era of antiretroviral therapy." Proceedings of the American Thoracic Society 8.3 (2011): 282-287.
Feldman, Charles. "Pneumonia associated with HIV infection." Current opinion in infectious diseases 18.2 (2005): 165-170.
Arora, V. K., and S. V. Kumar. "Pattern of opportunistic pulmonary infections in HIV sero-positive subjects: observations from Pondicherry, India." The Indian journal of chest diseases & allied sciences 41.3 (1998): 135-144.
Benito, Natividad, et al. "Pulmonary infections in HIV-infected patients: an update in the 21st century." European Respiratory Journal 39.3 (2012): 730-745.