What Is Another Name for Hartnup Disease? The Hartnup Disorder Explained

December 3, 2025 •

2 min read

According to the National Organization for Rare Disorders, Hartnup disease was first described in 1956 and is estimated to affect 1 in 30,000 individuals. A lesser-known metabolic condition, what is another name for Hartnup disease? It is also referred to as Hartnup disorder, a genetic condition impacting the body's ability to absorb certain amino acids.

Quick Summary

Hartnup disease, a genetic metabolic disorder, is also known as Hartnup disorder or pellagra-like dermatosis, among other names. It involves a defect in the transport of neutral amino acids, leading to pellagra-like symptoms and aminoaciduria.

Key Points

Alternative Names: Hartnup disease is also known as Hartnup disorder, pellagra-like dermatosis, and aminoaciduria, Hartnup type.
Genetic Cause: The disease results from mutations in the SLC6A19 gene, inherited in an autosomal recessive pattern.
Pathophysiology: A defective amino acid transporter impairs the absorption of neutral amino acids, particularly tryptophan, in the intestines and kidneys.
Symptomatic Attacks: Episodes of symptoms, including skin rash, ataxia, and psychiatric issues, are often triggered by stress, sun exposure, or poor nutrition.
Effective Management: Symptoms can be managed with a high-protein diet, niacin or nicotinamide supplementation, and sun protection.

Other Names for Hartnup Disease

Hartnup disease is an autosomal recessive metabolic disorder with several alternative names. Common names include Hartnup disorder or Hartnup syndrome. Other names, like Aminoaciduria, Hartnup type, highlight the excessive excretion of neutral amino acids in urine. Neutral 1 amino acid transport defect describes the malfunction of the B(0)AT1 transporter. Pellagra-like dermatosis emphasizes the sun-sensitive rash resembling pellagra. A more descriptive name is Pellagra-cerebellar ataxia-renal aminoaciduria syndrome, noting the rash, neurological issues like ataxia, and aminoaciduria.

The Genetic Basis and Pathology

Hartnup disease stems from mutations in the SLC6A19 gene on chromosome 5p15.33, which produces the B(0)AT1 amino acid transporter in the intestines and kidneys. This transporter is vital for absorbing neutral amino acids, particularly tryptophan, and reabsorbing them in the kidneys. Defective transport leads to poor absorption and excessive urinary excretion of these amino acids. The resulting tryptophan shortage impairs niacin (vitamin B3), serotonin, and melatonin synthesis, causing symptomatic episodes.

Intermittent Symptoms and Triggers

Not all individuals with Hartnup disease have symptoms, but some experience reversible episodes, often triggered by increased protein demand or metabolic stress.

Common triggers include:

Sunlight exposure
Poor nutrition or inadequate protein intake
Physical or emotional stress
Fever and illness
Certain medications, such as sulfonamides

Typical symptoms during an attack can include:

Photosensitive rash: A scaly, red rash on sun-exposed skin.
Cerebellar ataxia: Uncoordinated movements and unsteady gait.
Psychiatric symptoms: Mood changes, anxiety, delusions, and emotional lability.
Other neurological issues: Headaches, short stature, and fainting.

Diagnosis and Management

Diagnosis relies on detecting abnormal neutral amino acid excretion in urine. Genetic testing can confirm SLC6A19 mutations. Due to intermittent symptoms, a thorough evaluation is needed.

Management focuses on preventing and treating symptoms:

Dietary measures: A high-protein diet may help compensate for malabsorption.
Niacin supplementation: Oral nicotinamide helps treat pellagra-like symptoms.
Sun avoidance: Protection from sun is advised to prevent rash.
Symptomatic support: Neurological/psychiatric issues are managed with medication, often resolving with diet and nicotinamide.

For more detailed genetic information, refer to the National Institutes of Health (NIH) entry on Hartnup disease.

Comparison: Hartnup Disease vs. Classic Pellagra


Feature	Hartnup Disease	Classic Pellagra
Cause	Genetic mutation in SLC6A19 affecting amino acid transport.	Dietary niacin deficiency.
Core Problem	Defective neutral amino acid absorption/reabsorption.	Insufficient niacin/tryptophan intake.
Symptom Trigger	Intermittent attacks triggered by stress, sun, or poor nutrition.	Chronic wasting disease, triggers can worsen symptoms.
Associated Symptoms	Pellagra-like rash, cerebellar ataxia, psychiatric symptoms, and aminoaciduria.	Dermatitis, diarrhea, and dementia.
Underlying Mechanism	Tryptophan deficiency leads to reduced niacin synthesis.	Direct dietary deficiency of niacin/tryptophan.
Diagnosis	High levels of neutral amino acids in urine.	Clinical, confirmed by diet or response to niacin.

Conclusion

Beyond hartnup disease, names like Hartnup disorder, pellagra-like dermatosis, and aminoaciduria, Hartnup type describe this genetic condition. These names highlight its impact on amino acid transport, leading to tryptophan deficiency and symptoms affecting the skin and nervous system. Prognosis is generally good, with symptoms manageable through diet, niacin, and trigger avoidance.

Frequently Asked Questions

Hartnup disease is an autosomal recessive genetic disorder caused by mutations in the SLC6A19 gene, which codes for a protein responsible for transporting neutral amino acids.

This name is used because a common symptom of Hartnup disease is a sun-sensitive rash that closely resembles the dermatological symptoms of pellagra, a condition caused by niacin deficiency.

The most consistent diagnostic feature is the finding of neutral hyperaminoaciduria, or excessive excretion of neutral amino acids in the urine, which can be identified through urine chromatography.

No, a significant number of people with Hartnup disease remain asymptomatic throughout their lives, especially with an adequate diet.

Symptomatic episodes are typically treated with oral nicotinamide (a form of niacin) supplements. A high-protein diet and avoidance of sunlight are also key management strategies.

During an episode, a person may experience a red, scaly rash on sun-exposed areas, lack of coordination (cerebellar ataxia), mood swings, headaches, and tremors.

Yes, attacks of symptoms usually become progressively less frequent with age, and many individuals learn to manage their condition effectively over time.