As the FGFR1 and KLB variants are inherited in trans from each parent (Figure 2C), we hypothesized that a digenic inheritance model accounted for the phenotype with the variants in FGFR1 and KLB acting synergistically and leading to FGF21 resistance, thereby explaining the proband’s severe insulin resistance and tall stature. The gene discussed is FGFR1; the disease is Insulin resistance.