The analysis of lymphocyte subpopulations showed a reduction in number of B-cells (CD19+; median 0.02 G/L, range 0.01–0.03) and NK-cells (CD16+/CD56+; median 0.052 G/L, range 0.013–0.124) in the five patients studied; 3 of these patients also demonstrated T-cell deficiency (CD3+, median 1.14 G/L, range 0.44–1.71). The gene discussed is NCAM1; the disease is congenital T-cell immunodeficiency.