Fructose Metabolism Disorders

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.

Diagnosis and identification of heterozygous carriers of the mutated gene can also be made by direct DNA analysis. (Also see testing for suspected inherited disorders of metabolism Initial testing Most inherited disorders of metabolism (inborn errors of metabolism) are rare, and therefore their diagnosis requires a high index of suspicion. Timely diagnosis leads to early treatment and... read more .)

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.

This deficiency causes benign elevation of blood and urine fructose levels (benign fructosuria). 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 about 1/130,000 births.

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

This deficiency compromises gluconeogenesis and results in fasting hypoglycemia, ketosis, and metabolic acidosis Metabolic Acidosis Metabolic acidosis is primary reduction in bicarbonate (HCO3⁻), typically with compensatory reduction in carbon dioxide partial pressure (Pco2); pH may be markedly low or slightly... read more . This deficiency can be fatal in neonates. 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 unknown. Febrile illness can trigger episodes.

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