Glycogen Storage Disease IV
In a 16-month-old infant with a combination of hepatic and muscular features of glycogen storage disease IV (GSD4; 232500), Bruno et al. (1999) identified compound heterozygosity for a G-to-A transition in the GBE1 gene, resulting in an arg524-to-gln (R524Q) substitution, while the other allele was not expressed. The patient was the only child of healthy, unrelated parents. At birth he presented with severe hypotonia, flexion contractures of hips, knees, ankles, elbows, and wrists, and neck pterygium. At age 5 months, he was admitted to hospital for surgical correction of arthrogryposis. At that time, muscle hypotonia, stunted growth, hepatosplenomegaly, and liver dysfunction were noted. Laboratory investigations showed increased levels of liver enzymes, while serum creatine kinase remained normal. Electromyography showed a myopathic pattern, with pseudomyotonic discharges. The status of the patient at 22 months of age suggested that the liver dysfunction and the myopathy were static, that respiratory function was not affected, and that there was no abnormality of the heart or of mental development. In a follow-up study of the patient reported by Bruno et al. (1999), Bruno et al. (2004) identified a second GBE1 mutation on the other allele (607839.0014).
Adult Polyglucosan Body Neuropathy
In a non-Ashkenazi patient with adult polyglucosan body neuropathy (APBN; 263570), Ziemssen et al. (2000) identified compound heterozygosity for the arg524-to-gln mutation and an R515H mutation (607839.0019) in the GBE1 gene.
