T-Lymphocytopenia

Idiopathic CD4+ lymphocytopenia (ICL) is a depletion of CD4+ lymphocytes below 300 per cubic millimeter, or less than 20% of total lymphocytes, in the absence of HIV infection or other known causes of immunodeficiency. This is a rare, heterogeneous syndrome and does not appear to be caused by a transmissible agent. People with ICL are susceptible to opportunistic infections, namely, cryptococcus, atypical mycobacterial and Pneumocystis jiroveci pneumonia (PCP).

Criteria for diagnosis of idiopathic CD4 lymphocytopenia include:
 * CD4 cell count less than 300/mm3 or a CD4 percent less than 20 of total lymphocytes on two or more measurements
 * Lack of laboratory evidence of HIV infection
 * Absence of an alternative explanation for the CD4 lymphocytopenia

ICL is a rare disease; in 1993, a total of 47 confirmed cases were reported in a survey sponsored by the Centers for Disease Control. In contrast to the CD4 cell depletion caused by HIV, patients with idiopathic CD4 lymphocytopenia generally have a good prognosis.