Overview
Disorder of tryptophan metabolism is a rare group of inherited metabolic conditions in which the body cannot properly break down or use tryptophan, an essential amino acid found in many protein-rich foods. Tryptophan is important because the body uses it to make serotonin (a brain chemical that affects mood and sleep), niacin (vitamin B3), and other vital substances. When the enzymes responsible for processing tryptophan do not work correctly, harmful byproducts can build up in the body, or the body may not produce enough of the important chemicals it needs. Symptoms can vary widely depending on which specific step in the tryptophan pathway is affected. Some patients may experience skin rashes, sensitivity to sunlight, developmental delays, intellectual disability, problems with coordination, or psychiatric symptoms such as mood changes. In some forms, patients may develop pellagra-like symptoms due to niacin deficiency, including skin inflammation, diarrhea, and confusion. Hartnup disease is one of the better-known conditions in this group, where tryptophan and other amino acids are not properly absorbed in the gut and kidneys. Treatment is generally supportive and depends on the specific type of tryptophan metabolism disorder. It may include dietary modifications, niacin or nicotinamide supplementation, sun protection, and management of neurological or psychiatric symptoms. Early diagnosis and ongoing metabolic management can help improve quality of life and prevent complications.
Key symptoms:
Skin rash, especially after sun exposureSensitivity to sunlightRed, scaly skin similar to pellagraDiarrhea or loose stoolsIntellectual disability or learning difficultiesDevelopmental delays in childrenPoor coordination or unsteady walkingMood changes or emotional instabilityConfusion or difficulty thinking clearlyShort stature or poor growthSeizures in some casesFatigue or low energyUnusual urine odor or color
Variable
Can be inherited in different ways depending on the underlying gene
Variable
Can begin at different ages, from infancy through adulthood
FDA & Trial Timeline
3 eventsShanghai General Hospital, Shanghai Jiao Tong University School of Medicine
Tianjin Anding Hospital
McMaster University — NA
Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.
Treatments
No FDA-approved treatments are currently listed for Disorder of tryptophan metabolism.
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Treatment Centers
8 centersBaylor College of Medicine Rare Disease Center ↗
Baylor College of Medicine
📍 Houston, TX
🏥 NORDStanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
🔬 UDNUCLA UDN Clinical Site ↗
UCLA Health
📍 Los Angeles, CA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDMayo Clinic Center for Individualized Medicine ↗
Mayo Clinic
📍 Rochester, MN
👤 Mayo Clinic Center for Individualized Medicine
🏥 NORDUCLA Rare Disease Day Program ↗
UCLA Health
📍 Los Angeles, CA
Travel Grants
No travel grants are currently matched to Disorder of tryptophan metabolism.
Community
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Start the conversation →Latest news about Disorder of tryptophan metabolism
Disease timeline:
New recruiting trial: Tryptophan for Impaired AhR Signaling in Celiac Disease
A new clinical trial is recruiting patients for Disorder of tryptophan metabolism
Caregiver Resources
NORD Caregiver Resources
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Family & Caregiver Grants
Financial assistance programs specifically for caregivers of rare disease patients.
Social Security Disability
Learn how rare disease patients may qualify for SSDI/SSI benefits.
Questions for your doctor
Bring these to your next appointment
- Q1.What specific type of tryptophan metabolism disorder does my child or I have?,Which gene is affected, and what does that mean for our family?,What supplements or vitamins should be taken, and at what doses?,Are there specific foods to eat more of or avoid?,How much sun exposure is safe, and what precautions should we take?,Will this condition affect brain development or learning ability?,How often should we have follow-up appointments and lab tests?
Common questions about Disorder of tryptophan metabolism
What is Disorder of tryptophan metabolism?
Disorder of tryptophan metabolism is a rare group of inherited metabolic conditions in which the body cannot properly break down or use tryptophan, an essential amino acid found in many protein-rich foods. Tryptophan is important because the body uses it to make serotonin (a brain chemical that affects mood and sleep), niacin (vitamin B3), and other vital substances. When the enzymes responsible for processing tryptophan do not work correctly, harmful byproducts can build up in the body, or the body may not produce enough of the important chemicals it needs. Symptoms can vary widely depending
Which specialists treat Disorder of tryptophan metabolism?
7 specialists and care centers treating Disorder of tryptophan metabolism are listed on UniteRare, sourced from ClinicalTrials.gov principal investigators, published research, and the NPPES NPI registry.