Prenatal diagnosis of glycogen storage disorder type III

Spectrum of amyloglucosidase mutations in Asian Indian patients with Glycogen storage disease type III

Glycogen storage disease type III (GSD III) is a rare autosomal recessive inborn error of glycogen degradation pathway due to deficiency or reduced activity of glycogen debranching enzyme (GDE) that results in accumulation of abnormal glycogen in the liver, muscle, and heart. The cardinal hallmarks are hepatomegaly, fasting hypoglycemia, seizures, growth retardation, progressive skeletal myopathy, and cardiomyopathy in few. To date, 258 mutations in amyloglucosidase (AGL) gene have been identified worldwide. However, the mutation spectrum in the Asian Indian region is yet to be well characterized. We investigated 24 patients of Asian origin from 21 unrelated families with a provisional diagnosis of GSD III based on clinical and biochemical criteria. Molecular diagnosis was assessed by bidirectional sequencing and the impact of novel missense variants on the tertiary (three-dimensional) structure of GDE was evaluated by molecular modeling approach. Eighteen different pathogenic variants were identified, out of which 78% were novel. Novel variants included five nonsense, three small duplications and two small deletions, a splice site variant, and three missense variants. Variations in Exons 4, 14, 19, 24, 27, and 33 accounted for 61% of the total pathogenic variants identified and Allele p.Gly798Alafs*3 showed a high allele frequency of 11%. Molecular modeling study of novel pathogenic missense variants indicated the probable underlying molecular mechanism of adverse impact of variations on the structure and catalytic function of human GDE. Our study is the first large study on GSD III from the Asian subcontinent, which further expands the mutation spectrum of AGL.

Prevalence and clinical profile of glycogen storage diseases in children from Western India

Aim of the study

To determine the prevalence and clinical profile of glycogen storage diseases (GSD) in children in western India.

Material and methods

This retrospective analysis was conducted over a period of 7 years from 2006 to 2012. All children diagnosed with GSD on liver biopsy were included in the study. Their clinical history, examination, biochemical profile and outcome were noted.

Results

Of 751 children, 18 (2.4%) were clinically diagnosed with GSD. Mean age at presentation was 2.3 ±1.3 years. Male : female ratio was 1 : 1. The main presenting features were abdominal distension in 15 (83.3%) patients, hepatomegaly in all 18 (100%), splenomegaly in 11 (61.1%) and jaundice in 2 (11.1%) patients. Four (22.2%) patients had delayed development. Four (22.2%) patients were siblings to an older affected child. Only 1 (5.6%) patient had portal hypertension and 2 (11.1%) had ascites. Only 1 (5.6%) patient had elevated bilirubin levels, 17 (94.4%) had elevated serum glutamic-oxaloacetic transaminase (SGOT) and all 18 (100%) patients had elevated serum glutamic-pyruvic transaminase (SGPT) levels. Nine (69.3%) patients of the 13 tested had acidosis, 1 (9.1%) had elevated uric acid, 2 (11.1%) had neutropenia, 8 (44.4%) experienced hypoglycemia, 4 (22.2%) patients had nephromegaly and only 1 patient showed evidence of cirrhosis in the liver biopsy. Fifteen (83.3%) patients were short. Three out of 6 patients tested had hypertriglyceridemia (50%). One (5.6%) patient died, 9 (50%) patients were lost to followup and the remaining 8 (44.4%) patients continued regular follow-up.

Conclusions

Metabolic acidosis, hypertriglyceridemia, short stature, and hypoglycemia are major problems in children with GSD. Most of the patients are referred late at the time of presentation.