Lysinuric Protein Intolerance and Hartnup Disease

Lysinuric protein intolerance (LPI) is an inherited aminoaciduria caused by defective cationic amino acid transport at the basolateral membrane of epithelial cells in intestine and kidney. LPI is caused by mutations in the SLC7A7 gene, which encodes the y+LAT-1 protein, the catalytic light chain subunit of a complex belonging to the heterodimeric amino acid transporter family. Symptoms usually begin after weaning with refusal of feeding, vomiting, and consequent failure to thrive. Hepatosplenomegaly, hematological anomalies, and neurological involvement including hyperammonemic coma will progressively appear. Lung involvement (specifically pulmonary alveolar proteinosis), chronic renal disease that may lead to end stage renal disease, and hemophagocytic lymphohistiocytosis with macrophage activation all represent complications of LPI that may appear at any time from childhood to adulthood. The great variability of the clinical presentation frequently causes misdiagnosis or delayed diagnosis. The basic therapy of LPI consist of a low-protein diet, low-dose citrulline supplementation, nitrogen-scavenging compounds to prevent hyperammonemia, lysine, and carnitine supplements.