Glycogen Storage Diseases
A constant glucose supply to the brain, RBCS, and adrenal medulla (the inner portion of adrenal gland) is essential for the proper metabolic functioning of the body. This supply begins in the small intestine, where transport proteins facilitate glucose uptake into the cells lining the gut. This glucose then enters the liver via blood circulation, and is stored in the form of glycogen. This glycogen breaks down into glucose, which is released into the blood in times of starvation, fasting, or when body suddenly demands energy. Muscle tissues also store glycogen, which degrades during exereises. Degradation of glycogen to glucose is facilitated by some enzymes, which if gets blocked results in accumulation of glycogen in the liver or muscles; thus resulting in Glycogen Storage Diseases (GSD).
Glycogen Storage Diseases - Biochemical Lesions and Characteristic Features
(I) von Gierke's disease (type 1 glycogenosis)
Enzyme Defect
Glucose 6-phosphatase
Organ(s) Involved
Liver, kidney, and intestine
Characteristic Features
Glycogen accumulates hepatocytes and renal enlarged liver and kidney. hypoglycaemia, academia. fasting lactic hyperlipidemia, ketosis, gouty arthritis.
(II) Pompe's discase
Enzyme Defect
Lysosomal α-1,4 glucosidase (acid maltase)
Organ(s) Involved
All organs
Characteristic Features-Glycogen accumulates in lysosomes in almost all the tissues, the heart is mostly involved, enlarged liver and heart, the nervous system is also affected, and death occurs at an early age due to heart failure.
(III) Cori's disease (limit dextrinosis, Forbe's disease)
Enzyme Defect- Amylo α-1,6- glucosidase (branching enzyme)
Organ(s) Involved-Liver, muscle, heart leucocytes
Characteristic Features-Branched-chain glycogen accumulates, liver enlarged. clinical manifestations are similar but milder compared to von Gierke's disease.
(IV) Anderson's disease (amylopectinos is)
Enzyme Defect Glucosyl 4-6 transferase (branching enzyme)
Organ(s) InvolvedMost tissues
Characteristic Features-A rare disease, glycogen, cirrhosis of the liver, and liver impairment in function.
(V) McArdle's disease (type glycogenosis)
Enzyme Defect-Muscle glycogen phosphorylase
Organ(s) Involved-Skeletal muscle
Characteristic Features-Muscle glycogen stores very high, not available during exercise, the subject cannot perform strenuous exercise, suffer from muscle cramps, blood lactate and pyruvate do exercise, and muscles may not increase after get damaged due to inadequate energy supply.
(VI) Her's disease
Enzyme Defect-Liver glycogen phosphorylase
Organ(s) Involved-Liver
Characteristic Features-Liver glycogen glucose enlarged, liver form and cannot (pyruvate lactate can be precursors for glucose). mild hypoglycaemia and ketosis seen, and not a very serious disease.
(VII) Tarui's disease
Enzyme Defect -Phosphofructoki nase
Organ(s) Involved-Skeletal muscle, erythrocytes
Characteristic Features-Muscle cramps due to exercise, blood lactate not elevated, and haemolysis occurs.
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