16W-0247 is an 8-year-old child who was followed for seizures, ataxia and learning disability but the diagnosis of neurofibromatosis type I was missed until exome sequencing revealed a previously known pathogenic mutation in NF1. 16W-0269 is a 6-year-old child who was managed for years as a case of Bartter syndrome but exome sequencing led to a change in management after revealing a pathogenic mutation in SLC26A3 thus establishing the correct diagnosis of chloride-losing diarrhea. The gene discussed is NF1; the disease is cerebellar ataxia.