The HBS1L:MYB locus has been linked to a number of hematological traits including fetal hemoglobin levels, red and white blood cell counts, and platelet counts by genome-wide association studies (GWAS) [24–27], and we have previously described a female child with no apparent hematological abnormalities carrying compound heterozygous mutations resulting in Hbs1L deficiency [23]. The gene discussed is HBS1L; the disease is hyperinsulinemic hypoglycemia, familial, 4.