LPI Explained by Wikipedia

Who knows, maybe I'll be faithful enough to this blog for the next years that my link below will become outdated. By that time when you click on the below link 5-10 years from now I have a feeling they'll know a bit more about LPI and have a different description (or hey, the link might not even exist anymore). So I figured I'd post what is currently written about LPI on the online Wikipedia dictictionary as I found this website did the best job description the disorder in "plain-man's" terms.


Lysinuric protein intolerance (LPI), also named hyperdibasic aminoaciduria type 2 or familial protein intolerance, is an autosomal recessive disorder of diamino acid transport. About 100 patients have been reported, almost half of them of Finnish origin.

In LPI urinary excretion of cationic amino acids (ornithine, arginine and lysine is increased and these amino acids are poorly absorbed from the intestine. Therefore, their plasma concentrations are low and their body pools become depleted. Deficiency of arginine and ornithine restricts the function of the urea cycle and leads to hyperammonemia after protein-rich meals. Deficiency of lysine may play a major role in the sketal and immunological abnormalities observed in LPI patients

The diagnosis is based on the biochemical findings (increased concentrations of lysine, arginine and ornithine in urine and low concentrations of these amino acids in plasma, elevation of urinary orotic acid excretion after protein-rich meals, and inappropriately high concentrations of serum ferritin and lactate dehydrogenase isoenzymes and the screening of known mutation of the causative gene from a DNA sample.

Infants with LPI are usually syptom-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, delayed bone age and spontaneous protein aversion. Forced feeding of protein may lead to convulsions and coma. Mental development is normal if prolonged episode of hyperammonemia can be avoided. Some patients develop severe pulmonary and renal complications.

Treatment of LPI consists of protein-restricted diet and supplementationwith oral citrulline. Citrulline is a neutral amino acid that improves the function of the urea cycle and allows sufficient protein intake without hyperammonemia. Under proper dietary control and supplementation, the majority of the LPI patients are able to have a nearly normal life.