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Hartnup disease
Hartnup disease is a metabolic disorder characterized by abnormal transport of certain amino acids in the kidney and gastrointestinal system
Prevalence
1-9 / 100 000
3,300–29,800
US Estimated
4,500–40,500
Europe Estimated
Age of Onset
Childhood
ICD-10
E72
Inheritance Pattern
Autosomal recessive
Mitochondrial/Multigenic
X-linked dominant
X-linked recessive
Rare View
Hartnup Disease is a rare genetic metabolic disorder affecting the absorption of neutral amino acids, particularly tryptophan, in the intestine and kidneys. It is caused by mutations in the SLC6A19 gene, leading to niacin deficiency, which can result in symptoms similar to pellagra.
5 Facts you should know
FACT
Hartnup Disease is a rare, autosomal recessive disorder characterized by the impaired absorption of certain amino acids, particularly tryptophan, from the intestines and kidneys
FACT
It is caused by mutations in the SLC6A19 gene, affecting the transportation of amino acids across cell membranes, leading to tryptophan deficiency
FACT
Symptoms may vary widely but often include skin rash when exposed to sunlight (pellagra-like symptoms), neurological issues, such as ataxia and tremors, and psychiatric manifestations
FACT
Diagnosis involves clinical evaluation, urine tests demonstrating amino acid abnormalities (low levels of tryptophan), and genetic testing to confirm mutations in the SLC6A19 gene
FACT
5
Treatment involves managing symptoms through dietary modifications, including increased tryptophan intake, nicotinamide supplements to alleviate skin symptoms, and monitoring for associated complications
Interest over time
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Common signs & symptoms
Photosensitive dermatitis (pellagra-like), classically on sun-exposed areas
Intermittent episodes precipitated by illness, malnutrition, stress
Cerebellar ataxia, gait instability, tremor
Neuropsychiatric symptoms (irritability, mood changes; variable)
GI symptoms may occur during episodes (e.g., diarrhea) in some patients
Lab hallmark: neutral aminoaciduria; supportive testing may include low niacin status/tryptophan issues
Current treatments
Nicotinamide (niacinamide) supplementation (preferred over niacin to avoid flushing)
High-protein/nutritionally adequate diet; avoid prolonged fasting
Sun protection; manage triggers (intercurrent illness)
Symptom-directed support during acute episodes
References:
- Orphanet. Hartnup disorder (prevalence estimate)