It is possible that the two variants present in P1 p.(Arg56*) and p.(Arg69Cys) affect different functions of BCS1L. The p.(Arg56*) variant has been previously identified in a British patient that presented with Complex III deficiency and GRACILE syndrome (aminoaciduria, hypotonia, seizures, increased lactate) accompanied by an early death at the age of 2 days. The gene discussed is BCS1L; the disease is hyperinsulinemic hypoglycemia, familial, 4.