Lysinuric proteinintoleranceE72.-

LPI is mainly seen in Italy and Finland.In these countries the prevalence is 1:60,000

In LPI, the cationic ('basic') amino acids are excreted more in the urine and reabsorbed less in the intestine. At the same time, there is orotaziduria. These findings are due to a transport defect of cationic amino acids in the basolateral membrane of renal and intestinal epithelial cells caused by mutations in the SLC7A7 gene (14q11.2), which encodes a transporter complex (transporter 7 of the 'solute carrier family 7A').

Symptoms of LPI include vomiting, diarrhea, failure to thrive, hepato-splenomegaly, bone marrow abnormalities, osteopenia, episodes of hyperammonemic coma, mental retardation, altered immune response, chronic kidney disease, and lung involvement (mainly pulmonary alveolar proteinosis - PAP, less commonly interstitial lung disease). Lung involvement is a major cause of unfavorable course and lethal outcome.

Amino acid analysis reveals increased urinary excretion and decreased plasma concentrations for lysine, arginine, and ornithine.

Prognosis varies and is determined by pulmonary complications.

Patients receive a low-protein diet and additional administration of lysine, ornithine, and citrulline. Pulmonary alveolar proteinosis can be successfully treated with complete lung lavage according to literature reports.

1. Font-Llitjos M et al. (2009) Novel SLC7A7 large rearrangements in lysinuric protein intolerance patients involving the same AluY repeat. Europ J Hum Genet 17: 71-79.
2. Kato T et al (1982) Renal transport of lysine and arginine in lysinuric protein intolerance. Europ J Pediat 139: 181-184.
3. Kekomaki M et al (1968) Familial protein intolerance with deficient transport of basic amino acids. Report on an adult patient with chronic hyperammonemia Acta Med Scand 183: 357-359.
4. Noguchi A et al. (2019) Overview of symptoms and treatment for lysinuric protein intolerance. J Hum Genet 64:849-858.