Lysinuric protein intolerance (LPI) is an autosomal recessive[1] metabolic disorder affecting amino acid transport.

Infants with LPI are usually symptom-free when breastfed because of the low protein concentration in human milk, but develop vomiting and diarrhea after weaning.

The patients show failure to thrive, poor appetite, growth retardation, enlarged liver and spleen, prominent osteoporosis and osteopenia,[4] delayed bone age and spontaneous protein aversion.

[5] LPI is caused by mutations in the SLC7A7 gene, which encodes for a protein involved in the transport of amino acids across cell membranes.

Mutations in this gene impair the transport function, leading to the characteristic amino acid imbalances seen in LPI patients.