Conditions · Metabolism: carbohydrates and glycogen
Hereditary fructose intolerance !
In hereditary fructose intolerance, fruit, sugar or honey cause vomiting, hypoglycaemia and liver and kidney damage.
Updated 2026-11-01
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In biochemistry
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What it is
Inborn error of metabolism caused by lack of aldolase B (ALDOB gene). Symptoms start when the baby receives fructose, sucrose or sorbitol, usually with complementary feeding.
Who gets it
About 1 in 20,000 to 30,000 people worldwide.
Causes
- Autosomal recessive inheritance: ALDOB gene variants (A149P commonest in Europe)
Risk factors
- Carrier parents or affected siblings
- Exposure to fructose, sucrose or sorbitol (trigger)
Pathophysiology
Fructokinase keeps turning fructose into fructose 1-phosphate, but without aldolase B it accumulates in liver, kidney and intestine. It traps phosphate: ATP falls, nucleotides are broken down (high uric acid) and glycogen phosphorylase and gluconeogenesis are halted, so hypoglycaemia appears. ATP shortage damages hepatocytes and the proximal tubule (Fanconi syndrome).
Symptoms and signs
- Vomiting, abdominal pain and sweating after fruit, juice or sugary foods
- Hypoglycaemia with drowsiness or seizures
- Failure to thrive and jaundice
- Spontaneous aversion to sweets; teeth without caries
Diagnosis
- Clinical
- Symptoms that appear after fructose and disappear when it is removed; aversion to sweet foods.
- Tests
- During exposure: hypoglycaemia, hypophosphataemia, high uric acid, raised transaminases, abnormal clotting and signs of tubulopathy in urine. ALDOB gene testing. Fructose loading tests are no longer recommended because of their risk.
- Imaging
- Abdominal ultrasound: large or fatty liver; sometimes nephrocalcinosis.
Treatment
- Lifestyle
- Lifelong removal of fructose, sucrose and sorbitol from the diet, with dietitian support
- Medical
- Check that medicines and syrups contain no sucrose, fructose or sorbitol; vitamin supplements because of the fruit-free diet
- Acute
- Intravenous glucose and removal of fructose in a crisis
- Follow-up
- Monitoring of growth, liver and kidney
Complications
- Acute liver failure
- Renal Fanconi syndrome
- Fatty liver
- Death if fructose or sorbitol infusions are given
Prognosis
With a strict diet the outlook is excellent and growth is normal.
Test yourself
Think of the answer, then tap the question to see it.
Which enzyme is missing in hereditary fructose intolerance?
Aldolase B of liver, kidney and intestine.
Why does the patient with hereditary fructose intolerance become hypoglycaemic?
Fructose 1-phosphate traps phosphate and halts glycogen phosphorylase and gluconeogenesis.
Which dental finding is typical in these patients?
They have almost no caries, because they avoid sugar.
Which component of syrups and infusions is dangerous besides fructose?
Sorbitol, which the body turns into fructose, and sucrose.
Related conditions
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Hereditary fructose intolerance: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026); Hereditary fructose intolerance: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026); ALDOB gene: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).
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