Given the prevalence of T-cell abnormalities among patients with CVID, the recent redefinition of CVID by the ESID now emphasises on the use of T-cell immunophenotyping during the diagnostic workup.73 However, while there is a sound rationale to exclude patients with recurrent opportunistic infections and late-onset combined immunodeficiency,74 the arbitrary cut-offs for CD4 lymphopenia and naïve T-cell lymphopenia will exclude a proportion of patients (box 1). The gene discussed is CD4; the disease is common variable immunodeficiency.