ZAP-70 deficiency is a rare autosomal recessive form of combined immunodeficiency (CID) characterized by selective absence of circulating CD8 T cells with low, normal, or increased CD4 T cells in peripheral blood. Up to now, 14 unique mutations in the ZAP70 gene have been identified in patients with ZAP-70-related CID. We present a 3-year-old boy with a history of recurrent bacterial infections and autoimmunity. Initial laboratory findings showed a normal total lymphocyte count, but low levels of CD8 and CD4 T cells and an abnormal lymphocyte proliferation response. Immunoglobulin levels were normal, but the specific antibody response was impaired. Whole exome sequencing revealed a mutation within the kinase domain of ZAP-70. ZAP-70 deficiency should be considered in infants and young children with recurrent bacterial infections, in spite of having palpable lymph nodes, a notable thymus shadow, and a normal total lymphocyte count.
Keywords: Immunodeficiency; ZAP-70; lymphocyte.