Isolated lysine excretion in two cases of lysinuric protein intolerance (LPI), Murcia, Spain

Lysinuric protein intolerance (LPI) is a rare inherited metabolic disease, caused by a defective transport of dibasic aminoacids. Failure to thrive, hematological abnormalities, hepatosplenomegaly and hyperammonemic crisis are major clinical features. Urine concentration of cationic amino acids (arginine, ornithine and especially lysine) are increased while plasma dibasic amino acids are usually decreased. Plasma concentrations of LDH, ferritin, TBG, triglycerides and cholesterol are frequently observed. Recently two siblings were diagnosed of LPI in Murcia, Spain. The elder boy presented symptoms of protein malnutrition, enlarge liver and failure to thrive at the moment of diagnosis while her sister was asymptomatic. They were diagnosed by biochemical assays as both children presented hyperammonemia and an intermittent excretion of lysine in urine while arginine and ornithine urine and serum amino acids concentration were normal. Orotic and uracil excretion were also increased in the elder sibling, who showed clinical and biochemical improvement with a low protein diet and oral supplementation of citrulline, carnitine and calcium vitamin. In acute hyperammonemic crises we infused arginine until the symptoms had subsided and nitrogen scavenger drugs including sodium benzoate and sodium phenylpyruvate orally were prescribed too. The genetic analysis showed the c.625+1G>A mutation in homozygous in the SLC7A7 gene.