I've encountered the term 'Saccharopinuria' while reading about medical topics. What does it refer to exactly?
Saccharopinuria (an excess of saccharopine in the urine), also called saccharopinemia, saccharopine dehydrogenase deficiency or alpha-aminoadipic semialdehyde synthase deficiency, is a variant form of hyperlysinemia. It is caused by a partial deficiency of the enzyme saccharopine dehydrogenase, which plays a secondary role in the lysine metabolic pathway. Inheritance is thought to be autosomal recessive, but this cannot be established as individuals affected by saccharopinuria typically have only a 40% reduction in functional enzyme.

See also
Hyperlysinemia

References
External links
Saccharopinuria; Alpha-aminoadipic semialdehyde synthase deficiency at NIHs Office of Rare Diseases