ESPE Abstracts

Introduction: Lysinuric protein intolerance (LPI) is a rare autosomal recessive condition caused by a mutation in the SLC7A7 gene. This gene provides instructions for production of y+LAT-1 protein transporter, without which there is disruption in transportation of important amino acids, namely lysine, arginine and ornithine. This results in a body depletion of these amino acids, resulting in insidious symptoms such as short stature, muscle weakness and bone fragility, or with an acute episode of hyperammonaemia. There are only around 200 cases reported worldwide.

Case: We present a case of a 2 year old boy who attended the endocrine bone clinic following 2 fractures- one at 5 months old, the next at 13 months. A full child protection medical was unremarkable and referral was made due to a finding of osteopenia on X-rays.

Background: This patient was born to consanguineous Pakistani parents at term with a birth weight of 3 kg. There were no issues during pregnancy. 2 older siblings were fit and well. Weaning was challenging, and he remained predominantly breast fed at 2 years of age. He had slightly delayed speech and started walking at 1 year 9 months. His height and weight at time of presentation were <0.4^th centile. Baseline tests including bone profile, PTH, vitamin D and magnesium were all normal. Significant investigation results included low plasma levels of ornithine, lysine and arginine but with high levels of the same in the urine- extremely high in the case of lysine (1156umol/mmol, normal being <48). He also had raised LDH and ferritin. Ammonia was normal but plasma glutamine was high which can indicate fluctuating ammonia levels. This led to a diagnosis of lysinuric protein intolerance (confirmed with genetic testing) and he was referred to the metabolic team. He started on a protein-restricted diet and continues to undergo follow up with endocrinology for his osteopenia and short stature, with possibility of growth hormone in future as he remains <0.4^th centile for height and weight. Due to his risk of hyperammonaemia he was also started on L-citrulline and may start lysine supplementation in future to help with growth.

Conclusion: LPI is a rare metabolic disorder, that typically presents with diarrhoea and vomiting after weaning or episodes of lethargy after a protein rich meal. His failure to wean may have prevented acute hyperammonaemia. This is one of the first reported cases to have presented with fractures in the first year of life.