Clinical manifestation is highly variable. The
descriptions range from symptom-free to severe developmental delay, spastic
diplegia, seizures, rigidity, coma, episodic vomiting, and diarrhea. In one
case, coma and hyperammonia resolved with a low-protein diet. However, it
now seems that hyperlysinemia is not associated with an ill effect in the
majority of cases. A special diet seems not indicated, but some physicians
prefer to limit protein intake in their patients.