Cystathioninuria

Cystathioninuria is a rare inherited metabolic condition characterized by elevated levels of cystathionine in the urine. It is caused by a deficiency of the enzyme cystathionine gamma-lyase (also known as cystathionase), which is responsible for converting cystathionine to cysteine in the transsulfuration pathway of methionine metabolism. This enzyme deficiency leads to accumulation of cystathionine in body fluids and its excretion in the urine. Cystathioninuria is widely considered a benign biochemical condition rather than a clinically significant disease. It was initially identified through newborn screening programs and metabolic investigations, but extensive follow-up studies have not established a consistent association with specific clinical symptoms or disease manifestations. Some early reports suggested possible associations with intellectual disability or other neurological findings, but these associations have not been confirmed and are generally attributed to ascertainment bias, as affected individuals were often identified during evaluation for other conditions. The condition is inherited in an autosomal recessive manner and is caused by mutations in the CTH gene located on chromosome 1p31.1. In many cases, the enzyme deficiency is responsive to pyridoxine (vitamin B6), which serves as a cofactor for cystathionase. Administration of pyridoxine can reduce or normalize cystathionine levels in urine and plasma. However, given the benign nature of the condition, treatment is generally not considered necessary. Cystathioninuria may also occur transiently in premature infants due to developmental immaturity of the cystathionase enzyme, which normally increases in activity after birth.

Common questions about Cystathioninuria