In fact, in a hematological analysis of patients with ARPC1B deficiency, we found high absolute counts for transitional B cells of 123 × 106/L and 101 × 106/L for patients 2 and 3, respectively, well above the reference range and that of heathy age-matched controls that were 41 × 106/L. Here, ARPC1B is linked to hyperinsulinemic hypoglycemia, familial, 4.