Metabolic Disease With Autoimmune Phenomena: Two Cases of SLE-Like Disease in Young Children Diagnosed With Lysinuric Protein Intolerance

The document described two cases of young children with lysinuric protein intolerance, a rare metabolic disease, presenting with symptoms resembling systemic lupus erythematosus (SLE). The first case involved a boy with failure to thrive and various symptoms, including hemolytic uremic syndrome-like disease and lupus nephritis, who tested positive for several autoantibodies. The second case was a Turkish girl with polyarthritis, fatigue, diffuse hair loss, and other symptoms, also showing positive autoantibodies. Both children were diagnosed with a lupus-like disease and treated with immunosuppressive therapy. Metabolic studies revealed low serum levels and high urine levels of arginine, lysine, and ornithine, leading to the diagnosis of lysinuric protein intolerance. The second case was confirmed by identifying a new mutation in the SLC7A7 gene.