<prompt> A person having CD4 count of 200 presents with difficulty of breathing. The most probable diagnosis is?TuberculosisHistoplasmosisCandidiasisPneumocystis jiroveci  <response>: Pneumocystis pneumonia is the most common oppounistic infection associated with AIDS. The risk of Pneumocystis jiroveci pneumonia among HIV- infected patients rises markedly when circulating CD4 T cell counts fall below 200 cellsL. Tuberculosis in HIV patients occur when CD4 count is 100 cellsL. Ref: Manual of Emergency Medicine edited by Jon L. Jenkins, G. Richard Braen, 2004, Page 302 ; Harrisons Principles of Internal Medicine, Volume 2, Page 1267 ; Harrisons 17th ed chapter 182 