Novel missense mutations in the glycogen-branching enzyme gene in adult polyglucosan body disease

We describe the first non-Ashkenazi patient with adult polyglucosan body di sease and decreased glycogen-branching enzyme (GBE) activity in leukocytes. Gene analysis revealed compound heterozygosity for two novel missense muta tions Arg515His and Arg524Gln in the GEE gene. Both missense mutations are predicted to impair GEE activity. This is the first identification of GBE m utations underlying adult polyglucosan body disease in a non-Ashkenazi fami ly, and confirms that adult glycogen storage disease type IV can manifest c linically as adult polyglucosan body disease.