A group of inherited metabolic disorders which have in common elevations of serum LYSINE levels. Enzyme deficiencies of alpha-aminoadipic semialdehyde dehydrogenase and the SACCHAROPINE DEHYDROGENASES have been associated with hyperlysinemia. Clinical manifestations include mental retardation, recurrent emesis, hypotonia, lethargy, diarrhea, and developmental delay. (From Menkes, Textbook of Child Neurology, 5th ed, p56)