Although documented to have TPP1 enzymatic deficiency and/or TPP1 variants, individuals with atypical phenotypes are reported to have variable age of onset, variable symptomatology, and/or a protracted disease course.4,10,12, , , , , , , , , , , -24 Documented symptoms have included ataxia, gait disturbances, coordination difficulties, and cognitive regression, but seizures and visual findings are less frequently reported. The gene discussed is TPP1; the disease is hyperinsulinemic hypoglycemia, familial, 4.