ICL is a rare and heterogeneous T-cell immunodeficiency syndrome of unknown origin with repeatedly low levels of CD4+ T-cells (<300 μl−1 or <20 % of total lymphocytes), and no evidence of human immunodeficiency virus (HIV) infection (Régent et al., 2014; Smith et al., 1993).The differential diagnosis of ICL remains a challenge as it involves a wide range of analyses in different specialty areas such as immunology, haematology, rheumatology and infectious diseases (Zonios et al., 2012). The gene discussed is CD4; the disease is idiopathic CD4 lymphocytopenia.