Clinicopathological analysis of the homozygous p.W1327X AGL mutation in glycogen storage disease type 3

Abstract

We report on clinicopathological and whole body MRI analyses of the index patient of a large nonconsanguineous German-Ukraine family with homozygous and heterozygous AGL gene mutations at position p.W1327X (c.3980G > A). There are only limited reports on this phenotype with a homozygous genotype. The index patient, a 49-year-old woman presented with hepatomegaly, cardiomyopathy and moderate progressive proximal limb myopathy. Skeletal muscle showed severe vacuolar myopathy with storage of PAS-positive non-membrane-limited glycogen. An increase in glycogen content and completely decrease of debranching enzyme activity was measured in erythrocytes. Mutational analysis of the AGL gene showed a homozygous p.W1327X mutation. In the family, two brothers had been affected by severe infantile onset hepatomegaly and died within their first years of life by fatal liver cirrhosis. Furthermore, another sister severely affected by hepatomegaly, cardiomyopathy and proximal skeletal myopathy died at age 33. Three younger heterozygous sisters and a brother noticed exercise-induced myalgia and weakness since their teens. In sum, a homozygous p.W1327X mutation leads to a severe generalized glycogenosis types 3a and 3b within the same family. Even heterozygous p.W1327X mutation carriers may present with mild non-progressive neuromuscular symptoms, such as exercise-induced myalgia and fatigue.