IRIS-KS is not a specific entity but it is a phenomenon which can be recognized by certain well defined circumstances: the presence of low CD4+ T cell counts at the time of introduction of HAART; a temporal relationship between rapid clinical progression of KS and the development of new KS lesions usually of about 8 weeks (though this period may range from 3 weeks to 22 weeks) after the initiation of HAART; and the suppression of HIV load and restoration of CD4+ T cell count. Here, CD4 is linked to Kaposi's sarcoma.