In Richard Davenport’s description of an individual with ataxia harbouring an FMR1 gene permutation in the October issue of Practical Neurology,¹ the patient’s detailed family history is not explored. This may occasionally provide a clue to the diagnosis. I am seeing a late middle-aged patient with a seven year history of tremor and ataxia, whose diagnosis emerged when her daughter’s son was diagnosed with fragile X syndrome. (In a case report entitled Genetics in reverse, Chinnery et al described a similar scenario.²) In Davenport’s case, one presumes that the diagnosis was achieved by applying the newly described test on a repository of undiagnosed patients’ DNA samples. Indeed he recommends retaining (DNA) samples on patients for future “diagnostic” use. The level of consent required for retaining and testing such specimens is not specified. As exemplified by FMR1 premutation cases, the implications on future …