A person having CD-4 count of 200 presents with the difficulty of breathing. Most probable diagnosis is?

The host factors that predispose to the development of Pneumocystis pneumonia (PcP) include defects in cellular and humoral immunity. The risk of PcP among HIV-infected patients rises markedly when circulating CD4+ T cell counts fall below 200/µL. Pneumocystis pneumonia is the most common opportunistic infection associated with AIDS. Pneumocystis pneumonia may be difficult to diagnose because the symptoms—fever, cough, and shortness of breath— are nonspecific. Other persons at risk for PcP are patients receiving immunosuppressive agents (particularly glucocorticoids) for cancer and organ transplantation; those receiving biologic agents such as infliximab and etanercept for rheumatoid arthritis and inflammatory bowel disease; children with primary immunodeficiency diseases; and premature malnourished infants.