This is congruent with the fact that penetrance is almost 100% by age 8 years in NF1 germline mutation carriers34 compared to penetrance of 50% by the third decade of life in individuals with germline TP53 mutations.35 However, the presence of astrocytoma unrelated to the optic pathway at this age is more consistent with the germline TP53 mutation harboured by this child, which was missed by the treating physicians given his characteristic NF1 clinical features. The gene discussed is TP53; the disease is astrocytoma (excluding glioblastoma).