Lysinuric protein intolerance

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Obesity, Sleep & Internal medicine
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Lysinuric protein intolerance
Synonyms	LPI
Pronounce
Specialty	Medical genetics
Symptoms	Failure to thrive, hepatosplenomegaly, osteoporosis, muscle weakness, pulmonary alveolar proteinosis
Complications	Renal failure, pulmonary fibrosis, neurological disorders
Onset	Infancy
Duration	Lifelong
Types
Causes	Mutations in the SLC7A7 gene
Risks
Diagnosis	Genetic testing, amino acid analysis
Differential diagnosis	Cystinuria, Hartnup disease
Prevention
Treatment	Dietary management, ammonia scavengers, supplementation with citrulline
Medication
Prognosis	Variable, depending on severity and management
Frequency	Rare
Deaths

Autosomal recessive inheritance pattern

Lysinuric protein intolerance (LPI) is a rare inherited metabolic disorder characterized by an inability of the body to properly digest certain protein building blocks (amino acids), specifically lysine, arginine, and ornithine. This condition is classified as a urea cycle disorder because it can lead to an excess of ammonia in the bloodstream (hyperammonemia) due to the body's inability to effectively remove waste products of protein metabolism.

Signs and Symptoms

The signs and symptoms of LPI typically become apparent after an infant is weaned and starts to consume more protein from the diet. These can include failure to thrive, muscle weakness (hypotonia), and developmental delay. Some affected individuals may have episodes of confusion or coma due to hyperammonemia, especially after consuming a protein-rich meal.

Causes

LPI is caused by mutations in the SLC7A7 gene. This gene provides instructions for making a protein that is involved in the transport of certain amino acids across cell membranes. Mutations in the SLC7A7 gene disrupt the normal function of this protein, leading to the characteristic features of LPI.

Diagnosis

Diagnosis of LPI is based on the clinical symptoms, biochemical analysis of blood and urine, and confirmed by genetic testing. The biochemical analysis typically shows increased levels of lysine, arginine, and ornithine in the urine.

Treatment

There is currently no cure for LPI. Treatment is aimed at managing the symptoms and preventing complications. This may include a low-protein diet, supplementation with citrulline or arginine, and medications to prevent or control hyperammonemia.

Prognosis

The prognosis for individuals with LPI varies. Some individuals have a normal lifespan with good quality of life, while others may have severe complications such as lung disease or kidney failure.

See also

• Urea cycle disorder
• Hyperammonemia
• SLC7A7

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