M. Kansasii pulmonary disease in idiopathic CD4+ T-lymphocytopenia

Cases of patients with markedly depressed CD4+ T-lymphocyte counts, with or without opportunistic infections, in the absence of any evidence of human immunodeficiency virus (HIV) have been described in recent years. In 1992, the definition of "idiopathic CD4+ T-lymphocytopenia" was formulated by the Centers for Disease Control and Prevention (CDC) of Atlanta (USA). The present case illustrates the occurrence of an unexplained Mycobacterium kansasii pneumonia in a white HIV-negative subject with a persistent depletion of CD4+ T-lymphocytes and suppression of cell-mediated immunity. To our knowledge, this is the first observation of idiopathic CD4+ T-lymphocytopenia with pulmonary mycobacteriosis due to Mycobacterium kansasii, and the sixth case of this kind of immunodeficiency described in Italy.