Objective: To determine the genetic basis of an unexplained multisystem neurological disorder affecting 2 siblings.
Design: Case reports and whole-exome DNA sequencing.
Setting: Neurogenetics clinic, Institute of Genetic Medicine, Newcastle upon Tyne, England.
Patients: Two adult siblings with a sensorimotor neuropathy, ataxia, and spasticity.
Main outcome measures: Clinical, neurophysiological, imaging, and genetic data.
Results: Novel compound heterozygous frameshift mutations were detected in the SACS gene of both siblings, predicted to drastically truncate the sacsin protein.
Conclusions: Whole-exome sequencing rapidly defined the genetic cause of the disorder, expanding the clinical phenotype associated with SACS mutations to include a severe sensorimotor neuropathy.