Abstract
Objective: To investigate the clinical features, skeletal muscle imaging, and muscle pathological characteristics of late-onset GSD IIIa caused by mutation of the AGL gene in adults.Methods: The clinical data, skeletal muscle imaging, pathological data, and gene test results of a family with late-onset GSD IIIa in adulthood were collected in detail in November 2019.Results: The proband is a 40-years-old male, who was admitted into our hospital due to a 2-years history of limb weakness. The proband was diagnosed with the following syndrome: he had a 15-years history of elevated muscle enzymes; the cranial nerve examinations showed no abnormal findings; the muscle tension in both upper and lower limbs was low, and tendon reflexes were absent; the proband's muscle strength was 5 in the proximal muscles and 4 in the distal muscles of the upper limbs, with 3 in the proximal muscles and 4 in the distal muscles of the lower limbs; Magnetic Resonance Imaging (MRI) revealed abnormally high signal intensity changes in the posterior thigh muscle group, and the posterior-medial calf muscle group; and vacuoles were evident in some muscle fibers biopsied from the gastrocnemius muscle. Periodic acid-Schiff staining stained the cytoplasm of muscle fibers a dark red color. The proband's older brother exhibited the same clinical features. DNA analysis identified mutations in the AGL gene in the proband, his older brother, and parents. The proband and his older brother both carried two compound heterozygous mutations, c.866G>A and c.2855_2856insT. Pedigree analysis demonstrated that c.866G>A and c.2855_2856insT mutations had been inherited from the mother and father, respectively.Conclusion: Late-onset GSD IIIa in adults is clinically characterized by muscle weakness, muscle atrophy, and mainly occurred in the posterior thigh muscle group. We also identified two novel compound heterozygous mutations (c.866G> A and c.2855_2856insT) in the AGL gene.
Highlights
Glycogen storage disease type III (GSD III) is a rare autosomal recessive genetic disorder caused by the deficiency of the glycogen debranching enzyme
This study reported a patient aged 40 years who was diagnosed as GSD IIIa by muscle biopsy
Our findings provide evidence of a wider spectrum of mutations in patients with GSD IIIa in the Chinese population
Summary
Glycogen storage disease type III (GSD III) is a rare autosomal recessive genetic disorder caused by the deficiency of the glycogen debranching enzyme. Due to this deficiency, the glycogen debranching enzyme cannot break down the chains of glycogen normally. The glycogen debranching enzyme cannot break down the chains of glycogen normally This causes glycogen accumulation in the liver, skeletal muscle, and myocardium, resulting in liver enlargement, fasting hypoglycemia, delayed normal growth, and progressive muscle weakness [1]. This study reported a patient aged 40 years who was diagnosed as GSD IIIa by muscle biopsy. Our findings provide evidence of a wider spectrum of mutations in patients with GSD IIIa in the Chinese population
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