The first publication of Kluin‐Nelemans from 1984 described a partial fD deficiency in a 40‐year‐old monozygous twin with upper and lower respiratory tract infections caused by H. influenzae, Proteus mirabilis and Pseudomonas aeruginosa since childhood.2 The gene discussed is ELP1; the disease is hyperinsulinemic hypoglycemia, familial, 4.