G6PD and hyperinsulinemic hypoglycemia, familial, 4: In a letter to the journal Lancet in 1961, Beutler, Fairbanks, and colleagues described the family pedigree and ascertained that despite the unexpected complete absence of G6PD activity in the red cells of the propositus, it was not possible for her to be homozygous for G6PD deficiency because she had two sons with normal red cell G6PD levels (Figure 5).Fairbanks recalled that each time he measured her red cell G6PD level the spectrophotometer registered slightly below zero.