We would like to thank Dr Perlman for her letter reminding us of the adult-onset form of hexosaminidase A deficiency. As she notes, this disorder may have features similar to Friedreich ataxia, motor neuron disease, or psychosis.1- 3 The phenotypes of both hexosaminidase A deficiency and Friedreich ataxia have expanded with better understanding of the genetic abnormalities, leading to substantial overlap, particularly early in the course of the illness. The availability of enzyme testing for hexosaminidase A deficiency in leukocytes makes it one of the few readily identifiable disorders imitating Friedreich ataxia. In conjunction with other clinically available tests, hexosaminidase A testing can be an effective tool in defining the disorders that mimic Friedreich ataxia.
Lynch DR, Farmer JM, Balcer LJ, Wilson RB. In reply. Arch Neurol. 2002;59(11):1832. doi: