Patient fibroblasts displayed severely impaired processing of p100 into p52 (p.H142R/p.P190L, p.G167R, and p.Y580C) and defective RelB translocation to the nucleus and DNA binding (p.H142R/p.P190L and p.G167R), together with low levels of VCAM1 upregulation upon Lt stimulation (p.Y580C), as observed in fibroblasts from patients with AR NIK deficiency (32). This evidence concerns the gene NFKB2 and hyperinsulinemic hypoglycemia, familial, 4.