Deficiency of enzymes that metabolize fructose may be asymptomatic or cause hypoglycemia.
Fructose is a monosaccharide that is present in high concentrations in fruit and honey and is a constituent of sucrose and sorbitol. Fructose metabolism disorders are one of the many carbohydrate metabolism disorders.
See also Approach to the Patient With a Suspected Inherited Disorder of Metabolism.
Fructose 1-Phosphate Aldolase (Aldolase B) Deficiency
This deficiency causes the clinical syndrome of hereditary fructose intolerance. Inheritance is autosomal recessive; incidence is estimated at 1/10,000 births (1). 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 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.
Diagnosis and identification of heterozygous carriers of the mutated gene can also be made by direct DNA analysis. (See also testing for suspected inherited disorders of metabolism.)
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.
Aldolase B deficiency reference
1. Pinheiro FC, Sperb-Ludwig F, Schwartz IVD. Epidemiological aspects of hereditary fructose intolerance: A database study. Hum Mutat. 2021;42(12):1548-1566. doi:10.1002/humu.24282
Fructokinase Deficiency
This deficiency causes benign elevation of blood and urine fructose levels (benign fructosuria). Inheritance is autosomal recessive; incidence is about 1/130,000 births (1).
The condition is asymptomatic and diagnosed accidentally when a non-glucose reducing substance is detected in urine.
Fructokinase deficiency reference
1. Kishnani P, Yuan-Tsong C: Disorders of Carbohydrate Metabolism. In Emery and Rimoin's Principles and Practice of Medical Genetics, ed 6, edited by Rimoin D, Pyeritz R, Korf B. Elsevier, 2013, pp. 1-36. doi:10.1016/B978-0-12-383834-6.00097-5
Fructose-1,6-Bisphosphatase Deficiency
This deficiency compromises gluconeogenesis and results in fasting hypoglycemia, ketosis, and metabolic acidosis. This deficiency can be fatal in neonates. Inheritance is autosomal recessive; incidence is unknown. Febrile illness can trigger episodes.
Acute treatment of fructose-1,6-bisphosphatase deficiency is oral or IV glucose. Tolerance to fasting generally increases with age.
More Information
The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
Online Mendelian Inheritance in Man (OMIM) database: Complete gene, molecular, and chromosomal location information
