PSMB6 and urea cycle disorder: The transporter y+LAT1 is expressed in enterocytes, renal tubular cells, and monocytes/macrophages and its deficiency causes a complex phenotype that includes intermittent hyperammonemia with intolerance to protein-rich food (due to a functional urea cycle disorder), failure to thrive, renal Fanconi syndrome, and severe/life-threatening symptoms that include pulmonary alveolar proteinosis and hemophagocytic lymphohistiocytosis [63].