Hypoascorbemia

Hypoascorbemia

Hypoascorbemia is a rare genetic condition characterized by the inability to synthesize ascorbic acid (vitamin C) due to a mutation in the gene encoding the enzyme L-gulonolactone oxidase. This condition is of particular interest because it highlights the evolutionary loss of vitamin C synthesis in humans and some other animals.

Overview

Hypoascorbemia results from a deficiency in the enzyme L-gulonolactone oxidase, which is crucial for the biosynthesis of ascorbic acid from glucose. This enzyme is functional in most mammals, allowing them to produce vitamin C endogenously. However, in humans, certain primates, guinea pigs, and some other species, this enzyme is non-functional due to genetic mutations, leading to a reliance on dietary intake of vitamin C.

Symptoms

The primary consequence of hypoascorbemia is the potential development of scurvy, a disease resulting from vitamin C deficiency. Symptoms of scurvy include:

• Fatigue
• Swollen and bleeding gums
• Joint pain
• Anemia
• Skin hemorrhages

Diagnosis

Diagnosis of hypoascorbemia is typically based on clinical symptoms and dietary history. Blood tests can measure vitamin C levels to confirm deficiency. Genetic testing can identify mutations in the L-gulonolactone oxidase gene, although this is not commonly performed due to the rarity of the condition.

Treatment

The treatment for hypoascorbemia involves the regular intake of vitamin C through diet or supplements. The recommended daily allowance (RDA) for vitamin C varies by age, sex, and life stage, but supplementation is often necessary to prevent deficiency in individuals with hypoascorbemia.

Evolutionary Perspective

The loss of the ability to synthesize vitamin C in humans and some other species is an example of a pseudogene formation. The L-gulonolactone oxidase gene is present but non-functional, classified as a pseudogene. This evolutionary change is thought to have occurred due to a diet rich in vitamin C, making endogenous synthesis unnecessary.

Related Conditions

• Scurvy: A disease caused by vitamin C deficiency.
• Pseudogene: A section of a chromosome that is an imperfect copy of a functional gene.

See Also

• Vitamin C
• Genetic Disorders
• Evolutionary Biology

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• Nishikimi, M., & Yagi, K. (1991). Molecular basis for the deficiency in humans of gulonolactone oxidase, a key enzyme for ascorbic acid biosynthesis. *American Journal of Clinical Nutrition*, 54(6), 1203S-1208S.
• Stone, I. (1972). *The Healing Factor: Vitamin C Against Disease*. New York: Grosset & Dunlap.

NIH genetic and rare disease info

• NIH info on Hypoascorbemia

Hypoascorbemia is a rare disease.