Hartnup disease affects both males and females of all ethnic backgrounds. The gene ALC6A19, located on chromosome 5, is associated with the disorder. Hartnup disease is inherited in an autosomal recessive pattern, meaning that an individual must inherit two copies of the defective gene (one from each parent) to have the disorder.
Diagnosis
Because Hartnup disease is inherited, individuals are born with the disorder, but many have no symptoms. Symptoms may occur in individuals with Hartnup disease who have exposure to sunlight, a febrile illness, and/or poor nutrition. Symptoms which occur with exacerbation of Hartnup disease are:
- Skin symptoms - The skin reddens after exposure to sunlight (known as photosensitivity). Additional sun exposure may lead to dry, scaly patches on the skin which resemble eczema or pellagra. Eventually there may be very light (hypopigmented) or very dark (hyperpigmented) areas of skin.
- Nervous system symptoms – The individual experiences muscle weakness and uncoordinated movements (cerebellar ataxia). There may also be tremulousness or double vision present.
Treatment
A high-protein diet compensates for the deficient processing of amino acids in the body. Individuals with Hartnup disease should protect themselves from sunlight with clothing, hats, sunglasses, and sunscreen. If skin symptoms appear, a dermatologist should be consulted for treatment. Taking nicotinic acid or nicotinamide 50-300mg per day provides relief from both the skin and nervous system symptoms if they occur.
Last updated 2/1/06
Information for this article was taken from:
Sekulovic, L. K. (2005). Hartnup disease. eMedicine, accessed at http://www.emedicine.com/derm/topic713.htm
