Lysinuric Protein Intolerance: Causes, Symptoms, and Treatment
Medically reviewed by Harsha Moole, MD, Internal Medicine. Last reviewed: October 2, 2026.
What kind of doctor treats Lysinuric Protein Intolerance?
A medical geneticist usually leads care for this inherited metabolic disease. Dietitians help plan safe meals, and specialists such as a lung, bone, or kidney doctor may be involved depending on symptoms. A direct primary care or concierge doctor can be a first stop for an evaluation and can refer you to a specialist when needed.
What it is
Lysinuric protein intolerance is a rare inherited condition. It affects how the body handles protein building blocks called dibasic amino acids, mainly lysine and arginine. People with this condition cannot absorb these substances well from food, and their kidneys also release too much of them into the urine, leaving the body without enough and causing problems in many organs. Signs often appear only after a baby is weaned and starts eating regular food.
Symptoms
Symptoms often begin after infancy, once the diet includes more protein, with vomiting, diarrhea, and poor appetite after protein-rich meals. Babies and children may fail to grow and gain weight as expected. Other problems can include an enlarged liver and spleen, weak and brittle bones, and low blood counts that cause tiredness. Some people develop lung disease, and weak immunity raises infection risk.
Causes and who gets it
The condition is caused by changes in a gene called SLC7A7, inherited from both parents, who are usually symptom-free carriers. It is very rare worldwide but more common in Finland, Japan, and parts of Italy.
How doctors diagnose it
Doctors look at symptoms, growth history, and blood and urine tests, which can show loss of lysine and arginine. Genetic testing that finds a change in the SLC7A7 gene confirms the diagnosis.
Treatment
Treatment focuses on diet and supplements. Patients take citrulline, which the body can use to make the missing amino acids, and eat limited amounts of protein. Cornstarch may help keep blood ammonia levels steady, and some people need medicines for lung or bone problems.
When to see a doctor
See a doctor if a child vomits often, refuses protein-rich foods, or is not growing as expected. Get help quickly for confusion, extreme tiredness, or breathing problems, which can signal high ammonia or lung disease.
How a direct primary care or concierge doctor fits in
A direct primary care doctor charges a flat monthly fee instead of billing insurance, while a concierge doctor usually charges more and works alongside insurance. Either type can coordinate care by handling routine monitoring, ordering lab work, managing diet questions, and keeping in close contact with the metabolic specialist, referring to a medical geneticist or other specialist when needed.
Common questions
Can lysinuric protein intolerance be cured?
There is no cure, because the gene change is permanent. Treatment can manage symptoms and help prevent complications, and how well a person does varies.
Why does eating protein cause problems?
The intestine cannot absorb certain amino acids from protein-rich foods, so the body loses them. Eating a lot of protein can also raise blood ammonia, a waste product that can cause vomiting and, in severe cases, confusion.
Can adults have this condition?
Yes. Some people are not diagnosed until adulthood, especially if childhood symptoms were mild. Adults may have lung disease, weak bones, or kidney problems before the cause is found.
Should family members be tested?
Brothers and sisters of an affected person have a chance of having it too. Genetic testing can show who carries the changed gene, and a genetic counselor can help families understand the results.
Sources
- NIH Genetic and Rare Diseases Information Center - Lysinuric protein intolerance
- MedlinePlus Genetics - Lysinuric protein intolerance
Medical Disclaimer
This content is for general educational and informational purposes only and is not medical advice. It is not a substitute for professional medical advice, diagnosis, or treatment, and reading it does not create a doctor-patient relationship. Always seek the advice of your physician or another qualified health provider with any questions about a medical condition, and never disregard or delay seeking professional advice because of something you read here. If you think you may have a medical emergency, call 911 (or your local emergency number) immediately.
