Summary about Disease
Hereditary Fructose Intolerance (HFI) is a rare, inherited metabolic disorder caused by a deficiency of the enzyme aldolase B. This enzyme is primarily found in the liver, kidney, and small intestine and is essential for breaking down fructose. When aldolase B is deficient, the body cannot properly metabolize fructose, leading to a buildup of fructose-1-phosphate. This buildup can cause various health problems, primarily affecting the liver and kidneys.
Symptoms
Symptoms of HFI typically appear when fructose or sucrose (which breaks down into fructose and glucose) is introduced into the diet, often during weaning in infancy. Common symptoms include:
Vomiting
Poor feeding/aversion to sweet foods
Irritability
Lethargy
Jaundice
Failure to thrive (poor weight gain and growth)
Abdominal pain
Hepatomegaly (enlarged liver)
Hypoglycemia (low blood sugar), which can lead to seizures or coma if severe
Renal tubular dysfunction (problems with kidney function)
Increased bleeding tendency
Causes
HFI is caused by mutations in the ALDOB gene, which provides the instructions for making the aldolase B enzyme. It is inherited in an autosomal recessive pattern. This means that an individual must inherit two copies of the mutated gene (one from each parent) to develop the disorder. Individuals who inherit only one copy of the mutated gene are carriers but do not typically show symptoms.
Medicine Used
There is no specific medication to treat aldolase B deficiency itself. Treatment focuses on strict dietary management to avoid fructose, sucrose, and sorbitol. In cases of acute episodes of hypoglycemia, intravenous glucose may be administered. Medications might be used to manage specific complications, such as renal tubular dysfunction.
Is Communicable
No, HFI is not communicable. It is a genetic disorder that is inherited, not caused by an infectious agent.
Precautions
The most important precaution is strict adherence to a fructose-, sucrose-, and sorbitol-free diet. This involves:
Carefully reading food labels to identify hidden sources of fructose, sucrose, and sorbitol.
Avoiding fruits, honey, table sugar, high-fructose corn syrup, and many processed foods.
Consulting with a registered dietitian to develop a safe and nutritious diet.
Being cautious about medications, as some may contain sucrose or sorbitol.
Informing healthcare providers (doctors, dentists) about the condition.
How long does an outbreak last?
There are no "outbreaks" of HFI. It is a chronic condition that persists throughout life. Symptoms occur when fructose, sucrose or sorbitol is ingested. If these substances are avoided, the individual will generally be asymptomatic. Acute episodes of hypoglycemia or liver dysfunction can occur if fructose is accidentally ingested, and the duration of these episodes depends on the amount of fructose consumed and the promptness of treatment.
How is it diagnosed?
Diagnosis of HFI typically involves a combination of:
Clinical evaluation: Assessing symptoms, medical history, and family history.
Urine test: Detecting reducing substances (sugars) in the urine after fructose ingestion.
Liver biopsy: (Less common now) Historically used to assess aldolase B enzyme activity.
Genetic testing: Analyzing the ALDOB gene for mutations. This is the most reliable method of diagnosis.
Fructose tolerance test: (Rarely performed now due to risk) Involves administering a small dose of fructose and monitoring blood glucose levels and liver function.
Timeline of Symptoms
The timeline of symptoms depends on when fructose, sucrose, or sorbitol is introduced into the diet:
Infancy (during weaning): Symptoms typically begin when fruits, fruit juices, or other foods containing fructose or sucrose are introduced.
Childhood/Adulthood: Symptoms can appear at any age if fructose, sucrose, or sorbitol is ingested, even if the person was previously asymptomatic due to strict dietary adherence.
Acute exposure: Within hours of fructose ingestion, symptoms like vomiting, abdominal pain, and hypoglycemia can develop. Prolonged exposure can lead to liver and kidney damage.
Important Considerations
Early diagnosis and dietary management are crucial to prevent long-term complications such as liver and kidney damage.
Lifelong adherence to a strict fructose-, sucrose-, and sorbitol-free diet is essential.
Individuals with HFI should carry identification indicating their condition, especially in case of emergencies.
Genetic counseling is recommended for families with a history of HFI to assess the risk of having affected children.
Close monitoring by a physician and registered dietitian is necessary to ensure adequate nutrition and prevent complications.