SUMMARY
1. Lysinuric protein intolerance is an inborn error of metabolism disease with autosomal recessive inheritance.
2. Patients typically present during infancy after being weaned. Findings include vomiting, diarrhea, lethargy following protein-rich meals, poor feeding, failure to thrive, hepatosplenomegaly, and muscular hypotonia.
3. Immunologic abnormalities have been reported including lymphopenia, decreased CD4 T cell number, IgG subclass deficiency, and impaired specific antibody response. Decreased leukocyte phagocytic activity and severe Varicella infections have also been reported.
4. This disease is caused by mutations in the SLC7A7 gene. Defects in this gene result in defective transport of the dibasic amino acids lysine, arginine, and ornithine in the intestine and renal tubule, leading to low levels in the blood.
5. Patients with recurrent infections and significant antibody deficiency may be candidates for immunoglobulin replacement therapy.
OVERVIEW
Lysinuric protein intolerance is an inborn error of metabolism disease with autosomal recessive inheritance. Patients typically present during infancy after being weaned. Findings include vomiting, diarrhea, lethargy following protein-rich meals, poor feeding, failure to thrive, hepatosplenomegaly, and muscular hypotonia.
Immunologic abnormalities have been reported including lymphopenia, decreased CD4 T cell numbers, IgG subclass deficiency, and impaired specific antibody response. Decreased leukocyte phagocytic activity and severe Varicella infections have also been reported.
This disease is caused by mutations in the SLC7A7 gene. Defects in this gene result in defective transport of the dibasic amino acids lysine, arginine, and ornithine in the intestine and renal tubule, leading to low levels in the blood.
EVALUATION
Patients diagnosed with Lysinuric Protein Intolerance should have a complete immune evaluation.
Step 1: Immune Evaluation
-IgG, IgM, IgA
-IgG Subclasses
-Specific antibody responses to vaccine antigens
-CBC with Differential
-Lymphocyte subset enumeration by flow cytometry (CD3, CD4, CD8, CD19, CD16/56)
-Immunologic abnormalities reported in patients include IgG subclass deficiency, impaired specific antibody responses, lymphopenia, and decreased CD4 T cell number.
MANAGEMENT
Patients with recurrent infections and significant antibody deficiency may be candidates for prophylactic antibiotics or immunoglobulin replacement therapy.