Brain fog and protein logs: unravelling encephalopathy in lysinuric protein intolerance with rare mutation and expanded phenotypic spectrum

Lysinuric protein intolerance (LPI) is an autosomal recessive disorder caused by variants in the SLC7A7 gene, leading to impaired transport of dibasic amino acids across intestinal and renal membranes. This results in postprandial hyperammonaemia due to deficiencies in lysine, arginine and ornithine, crucial substrates for the urea cycle. It commonly presents in infancy with recurrent vomiting, diarrhoea and encephalopathy. Diagnosis involves molecular genetic testing for the SLC7A7 gene variant. In this case, the rarity of the neuroimaging findings and the identification of an ultra-rare mutation contribute to the expanding clinical and genetic spectrum of LPI. Despite therapeutic advancements, the prognosis of LPI hinges on the progression of pulmonary and renal complications, underscoring the importance of comprehensive care and monitoring.