Lysinuric protein intolerance

Lysinuric protein intolerance is an autosomal recessive metabolic disorder of amino acid transport, in which the body cannot properly digest and use certain proteins. It is caused by mutations in the SLC7A7 gene. Urinary loss of the cationic amino acids ornithine, arginine and lysine is increased and their absorption from the gut is poor, so blood levels fall, the urea cycle is restricted and ammonia can build up after protein-rich meals. Infants are usually symptom-free while breastfed and develop vomiting and diarrhoea after weaning, with failure to thrive, an enlarged liver and spleen, bone thinning and a spontaneous aversion to protein. About 140 patients have been reported, almost half of them of Finnish origin. Diagnosis rests on characteristic amino acid findings in urine and plasma.