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Fructose Metabolism Disorders

By

Matt Demczko

, MD, Sidney Kimmel Medical College of Thomas Jefferson University

Last full review/revision Apr 2020| Content last modified Apr 2020
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Deficiency of enzymes that metabolize fructose may be asymptomatic or cause hypoglycemia.

Fructose 1-phosphate aldolase (aldolase B) deficiency

This deficiency causes the clinical syndrome of hereditary fructose intolerance. Inheritance is autosomal recessive Autosomal Recessive Genetic disorders determined by a single gene (Mendelian disorders) are easiest to analyze and the most well understood. If expression of a trait requires only one copy of a gene (one allele)... read more ; incidence is estimated at 1/20,000 births. Infants are healthy until they ingest fructose; fructose 1-phosphate then accumulates, causing hypoglycemia, nausea and vomiting, abdominal pain, sweating, tremors, confusion, lethargy, seizures, and coma. Prolonged ingestion may cause cirrhosis, mental deterioration, and proximal renal tubular acidosis Type 2 (proximal) RTA Renal tubular acidosis (RTA) is acidosis and electrolyte disturbances due to impaired renal hydrogen ion excretion (type 1), impaired bicarbonate resorption (type 2), or abnormal aldosterone... read more with urinary loss of phosphate and glucose.

Diagnosis of fructose 1-phosphate aldolase deficiency is suggested by symptoms in relation to recent fructose intake and is confirmed by DNA analysis. Previous confirmatory testing used liver biopsy or induction of hypoglycemia by fructose infusion 200 mg/kg IV.

Short-term treatment of fructose 1-phosphate aldolase deficiency is glucose for hypoglycemia; long-term treatment is exclusion of dietary fructose, sucrose, and sorbitol. Many patients develop a natural aversion to fructose-containing food. Prognosis is excellent with treatment.

Fructokinase deficiency

The condition is asymptomatic and diagnosed accidentally when a non-glucose reducing substance is detected in urine.

Deficiency of fructose-1,6-biphosphatase

Acute treatment of fructose-1,6-biphosphatase deficiency is oral or IV glucose. Tolerance to fasting generally increases with age.

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