5th February 2024

Disorders of carbohydrate metabolism

Disorders of carbohydrate metabolism can occur in many forms, and they can be divided mainly into acquired or inherited (inborn). 

Acquired

Acquired forms of carbohydrate metabolism are more common, including diabetic ketoacidosis, hyperosmolar hyperglycaemic state and hypoglycaemia. 

Inherited

This section aims to describe common to rare inborn carbohydrate metabolism disorders. These conditions are usually present in children, and understanding the metabolic pathway affected is vital to understanding these conditions. Many of the clinical features of the inherited disorders of carbohydrate metabolism are caused by:

• Lack of glucose for body organ metabolism
• Inability to break down glucose to pyruvate
• Inability to oxidise pyruvate fully in the Krebs cycle

For the MRCP Part 1 exam, it is beneficial to know some (rare) disorders of carbohydrate metabolism (and its associated high-yield facts), which are favourites. 

Galactosaemia

Galactosaemia is a rare autosomal recessive condition due to the deficiency of galactose-1-phosphate uridylyltransferase, resulting in the accumulation of galactose-1-phosphate. This causes features such as:

• Jaundice and hepatomegaly
• Failure to thrive
• (Oil droplet) cataracts
• Hypoglycaemia after exposure to galactose
• Fanconi syndrome

Galactokinase deficiency

Galactokinase deficiency is an autosomal recessive disorder causing decreased conversion of galactose to galactose-1-phosphate. Galactokinase catalyses the first step of galactose phosphorylation in the Leloir pathway, and patients do not present with severe manifestations in early infancy. Important features include cataracts. Diet is the foundation of therapy, with the elimination of lactose and galactose sources being the definitive therapy.