She presented aged 3 weeks with a persistent maculopapular rash which developed into erythroderma unresponsive to emollients, and initial investigations identified eosinophilia and total lymphocytosis (9,037 cells/microlitre) despite low CD3 + CD8 + T-cells (69 cells/microlitre) and absent naïve T-cells (Table 1). The gene discussed is CD8A; the disease is Increased total eosinophil count.