Glycogen storage diseases (GSD) are a group of inherited disorders of metabolism that result in storage of excess glycogen. Several well defined defects in one of the enzymes involved in the synthesis or degradation of glycogen have been described. There are over 15 types and they are classified based on the enzyme deficiency and the affected tissue (liver, muscle or both).
In this study, we wish to report the biochemical investigations adopted in main infantile GSD diagnosed in our laboratory.
Four steps diagnostic procedure have been assumed, taking into account several frequent clinical observations leading to further targeted biochemical parameters:
Assessment of the metabolic disorders with standard tests (fast blood glucose, uric acid, triglycerides, total cholesterol, ASAT, ALAT, CK, lactic acid).
Quantitative determination of glycogen in leucocytes (or erythrocytes) after extraction, precipitation and treatment with an throne reagent.
Oral galactose test with blood lactate and glucose estimations, in combination with a glucagon tolerance test to screen the main types of liver glycogenosis.
Lysosomal acid a-glucosidase activity when GSD type II (Pompe disease) is suspected.
Since 1995 and on the basis of this screening procedure and clinical features, 14 cases of GSD have been categorised:
· 6 forbes’s disease (GSD III, debranching-enzyme deficiency)
· 3 von Gierke’s disease (GSD I, glucose-6-phosphatase deficiency)
· 2 pompe’s disease (GSD II, maltase acid deficiency)
· 1 Andersen’s disease (GSD IV, branching-enzyme deficiency)
· 1 Hers’s disease (GSD VI, hepatic phosphorylase deficiency)
· 1 GSD IX (phosphorylase kinase deficiency)
Our laboratory diagnostic approach include simple screening tests easy to implement in clinical chemistry laboratories. Thus, Pompe disease diagnosis is easily done in our laboratory. The measurement of tissue enzyme activities (liver and muscle) of the other enzymes is limited to some specialised laboratories. The molecular diagnosis offers a good alternative for GSD type 0, I and III but requires better financial means.