We report a case of a European Caucasian 27- year old woman with a primary HIV- infection presenting with extremely low CD4+ T cell count who developed a haemophagocytic syndrome after starting ART and in whom we documented a very unusual serological and virological response, characterized by an impaired HIV- antibody production and a 12 month time frame to reach an undetectable viral load, despite no evidence of resistance. The gene discussed is CD4; the disease is HIV infectious disease.