Makindo Medical Notes

💉 Glucagon may be ineffective in treating hypoglycaemia in glycogen storage diseases, as glycogen cannot be mobilised.

📖 About

• ⚡ Glycogen storage diseases (GSDs) can be divided into those affecting primarily muscle and those affecting the liver.
• 🔍 See also Von Gierke Disease entry.

🧬 Aetiology

• Glycogen = a high molecular weight polymer of glucose residues.
• 🏋️‍♂️ Muscle and 🫀 liver contain significant glycogen stores.
• 🔧 Enzymes: Glycogen formed by glycogen synthase, broken down by glycogen phosphorylase.

🧑‍⚕️ Clinical

• Most are autosomal recessive enzyme deficiencies.
• 🫀 Hepatomegaly is common (but ❌ no splenomegaly).
• ⚠️ Hypoglycaemia → drowsiness, seizures, failure to thrive.
• 📉 Lactic acidosis common in infancy presentations.
• 👶 Infants: poor growth, hypoglycaemia. 👦 Older children: hypotonia, muscle weakness, wasting.

⚠️ Complications (Long-Term)

• Severe hypoglycaemia → cerebral oedema, coma, death.
• 🫁 Hepatic tumours (adenoma/adenocarcinoma).
• 🩸 Glomerular hyperfiltration & glomerulosclerosis.
• 🧠 Brain damage, severe anaemia, growth failure.

🔑 Commoner Forms of GSD

• Type I – Von Gierke’s 🫀 Glucose-6-phosphatase deficiency → hepatomegaly, severe fasting hypoglycaemia, lactic acidosis. High mortality though some survive. Avoid fructose & galactose.
• Type II – Pompe’s ❤️ Acid maltase (lysosomal α-1,4-glucosidase) deficiency. Cardiomyopathy, hypotonia, enlarged tongue. Death in infancy. 💡 Mnemonic: “Pompe trashes the pump” (heart, liver, muscle).
• Type III – Cori’s 🧩 Debranching enzyme deficiency. Milder than Von Gierke’s, normal lactate, but risk of cardiomyopathy.
• Type IV – Andersen’s 🧒 Branching enzyme deficiency → hepatosplenomegaly, cirrhosis, failure to thrive. Often fatal in childhood. Neuromuscular form may present later.
• Type V – McArdle’s 🏃 Muscle glycogen phosphorylase deficiency. Painful muscle cramps, exercise intolerance, myoglobinuria (red urine), arrhythmias. “Second-wind phenomenon” during exercise. Normal life expectancy.

📌 Summary

GSDs are inherited disorders of glycogen metabolism → abnormal accumulation of glycogen in tissues. At least 15 types identified; Types I–V are the most important and are autosomal recessive. Diagnosis often via PAS stain of tissues to identify glycogen.

🧠 Mnemonic: “Vice President Can’t Accept Money” → Von Gierke (I), Pompe (II), Cori (III), Andersen (IV), McArdle (V).