C1‐INH deficiency can be proved with a complete complement laboratory testing (total classic complement cascade, C3, C4, C1‐INH concentration level and C1‐INH functional activity, anti‐C1‐INH antibodies [IgA, M, G]).5, 6, 7, 8. Here, SERPING1 is linked to hyperinsulinemic hypoglycemia, familial, 4.