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Hartnup disease
Last reviewed: 23.04.2024
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Hartnup disease is a rare disease associated with abnormal reabsorption and excretion of tryptophan and other amino acids. Symptoms of Hartnup disease include rash, CNS disorders, low growth, headaches, and fainting and collapse. The diagnosis is based on the determination of a high urinary content of tryptophan and other amino acids. Preventive treatment includes niacin or niacinamide, and in the course of the attacks, nicotinamide is prescribed.
What causes Hartnup disease?
Hartnup's disease is inherited by an autosomal recessive type. Developed reduced absorption in the small intestine of tryptophan, phenylalanine, methionine and other monoamino monocarboxylic amino acids. Accumulation of non-sucked amino acids in the gastrointestinal tract increases their metabolization by bacterial flora. Some degradation products of tryptophan, including indoles, kynurenin and serotonin, are absorbed in the intestine and appear in the urine. Also renal reabsorption of amino acids is disturbed, which causes generalized aminoaciduria, including all neutral amino acids, except proline and hydroxyproline. Also, the conversion of tryptophan to niacinamide is disrupted.
Symptoms of Hartnup disease
Almost always the appearance of symptoms is preceded by a low supply of nutrients. The symptoms of Hartnup's disease develop due to the deficiency of niacinamide and resemble the manifestations of pellagra, especially the rash in open areas of the body. Neurological manifestations include cerebellar ataxia and mental disorders. There is often a delay in mental development, low growth, headaches, collapoid conditions, fainting. Despite the fact that the disease is present at birth, the symptoms can appear in infancy, in childhood or in young adults. The appearance of symptoms can be provoked by insolation, certain medications or other stresses.
Diagnosis of Hartnup disease
The diagnosis is based on the detection of characteristic violations of excretion of amino acids in the urine. Indoles and other degradation products of tryptophan in urine are additional evidence of the presence of Hartnup disease.
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Treatment of Hartnup disease
Hartnup disease has a favorable prognosis, the frequency of attacks usually decreases with age. Attacks can be prevented by maintaining a good nutritional status and supplementing the diet with niacin or niacinamide, 50-100 mg orally 3 times a day. The developed attack is treated with nicotinamide, 20 mg orally once a day.
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