key term - Hartnup disease

Definition

Hartnup disease is a rare genetic disorder caused by a mutation in the SLC6A19 gene, which encodes a transporter responsible for the absorption of neutral amino acids in the kidneys and intestines. This disease is significant because it disrupts amino acid metabolism, particularly affecting the absorption of tryptophan, leading to a deficiency that can result in various clinical manifestations such as skin rashes and neurological symptoms.

5 Must Know Facts For Your Next Test

1. Hartnup disease is inherited in an autosomal recessive manner, meaning that both copies of the gene must be mutated for the disorder to manifest.
2. The condition can lead to symptoms such as photosensitivity, ataxia, and psychiatric issues due to low levels of tryptophan affecting serotonin production.
3. Diagnosis typically involves measuring amino acid levels in urine and blood, which show increased excretion of neutral amino acids.
4. Management of Hartnup disease often includes dietary adjustments to increase tryptophan intake and supplementation with nicotinamide to counteract potential deficiencies.
5. Despite its rarity, Hartnup disease illustrates the importance of amino acid transport in overall health and the interconnectedness of metabolic pathways.

Review Questions

• How does the genetic mutation associated with Hartnup disease affect amino acid metabolism?
  • The mutation in the SLC6A19 gene impairs the transport of neutral amino acids, especially tryptophan, leading to their decreased absorption in the intestines and kidneys. This deficiency disrupts normal metabolic processes since tryptophan is crucial for producing serotonin and other important compounds. As a result, individuals may experience various symptoms due to this metabolic imbalance.
• What clinical manifestations are commonly associated with Hartnup disease and how do they relate to nutrient deficiencies?
  • Common manifestations of Hartnup disease include skin rashes upon sun exposure (photosensitivity), ataxia, and mood disorders. These symptoms arise primarily from the deficiency of tryptophan, which affects serotonin levels, leading to neurological symptoms. Furthermore, inadequate absorption of other neutral amino acids can also contribute to muscle weakness and other systemic issues.
• Evaluate the management strategies for Hartnup disease and their effectiveness in alleviating symptoms.
  • Management strategies for Hartnup disease focus on increasing dietary intake of tryptophan and using nicotinamide supplements. These approaches aim to restore normal levels of tryptophan and reduce symptoms related to its deficiency. The effectiveness of these strategies has been observed in many patients who experience significant symptom relief and improved quality of life when adhering to dietary recommendations. Ongoing monitoring and adjustment of treatment plans are essential for optimizing patient outcomes.

Related terms

Neutral Amino Acids: A group of amino acids that are not charged and include essential amino acids like tryptophan, phenylalanine, and leucine, which are crucial for protein synthesis and metabolic functions.

Tryptophan: An essential amino acid that is a precursor for serotonin, melatonin, and niacin; it is significantly affected in Hartnup disease due to impaired absorption.

SLC6A19: The gene that encodes the neutral amino acid transporter, mutations in which lead to Hartnup disease and result in impaired transport of certain amino acids.