With the caveat that we have studied a relatively small cohort, and it would be interesting to analyze more GATA2 patients, our data strongly suggest that the, analysis of lymphocyte subsets can provide indispensable knowledge in the symptomatic and presymptomatic stage of patients with GATA2 deficiency that could help when HSCT is being considered soon after the diagnosis. This evidence concerns the gene GATA2 and hyperinsulinemic hypoglycemia, familial, 4.