Lysinuric protein intolerance: Pearls to detect this otherwise easily missed diagnosis.

Failure to thrive, chronic diarrhea, and hepatomegaly should raise suspicion for LPI. Urine amino acids can be normal in this condition in the setting of malnutrition, a common complication of the disease. Additionally, it has been previously shown that the plasma arginine and ornithine concentration is higher in LPI subjects.