Essential fructosuria

• Increased conversion of fructose to fructose-6-phosphate by hexokinase (hexokinase becomes the main pathway for turning fructose to fructose-6-phosphate)
• Unphosphorylated fructose does not get trapped in cells → remaining excess fructose → excretion of fructose in urine

Mnemonic

Fructokinase deficiency is kinder

Hereditary fructose intolerance

• Accumulation of fructose-1-phosphate → decrease in available phosphates → inhibition of glycogenolysis and gluconeogenesis → hypoglycemia
  • Phosphates are trapped in F-1-P, can’t be used in elsewhere
• Clinical features
  • Symptoms begin when the child is weaned off breast milk and starts consuming food that contains sucrose (e.g., fruit, juice, honey)
    • Fructose are like poisonous to them
  • Bloating, sweating, vomiting
  • Failure to thrive
  • Jaundice (can progress to cirrhosis)
  • Bleeding tendency
  • Severe hypoglycemia: seizures, hypotonia, poor feeding, cyanosis, irritability
  • Hepatomegaly
• Treatment: lifelong adherence to a fructose-free, sorbitol-free, and sucrose-free diet
  • Some of the ingested sorbitol gets broken down into fructose during digestion.
  • Sucrose, also known as table sugar, is a disaccharide sugar molecule. It’s made up of two simpler sugars: fructose and glucose.