Carnosinase deficiency

Carnosinase deficiency, also known as serum carnosinase deficiency or carnosinemia, is a rare inborn error of metabolism caused by a deficiency of the enzyme carnosinase (specifically serum carnosinase, encoded by the CNDP1 gene). Carnosinase is responsible for breaking down the dipeptide carnosine (beta-alanyl-L-histidine) and related dipeptides such as homocarnosine and anserine. When this enzyme is deficient, these dipeptides accumulate in the blood and are excreted in excess in the urine (carnosinuria). The condition primarily affects the nervous system. Clinical features reported in affected individuals include intellectual disability, seizures (myoclonic epilepsy), hypotonia, and developmental delay. Some patients may also exhibit tremor and sensory neuropathy. However, the clinical significance of carnosinase deficiency has been debated, as some individuals with biochemical evidence of the deficiency appear to be clinically asymptomatic. It is worth noting that serum carnosinase activity is normally low or absent in infants and young children, reaching adult levels only around age 10–15 years, which can complicate diagnosis in younger patients. There is currently no specific curative treatment for carnosinase deficiency. Management is primarily supportive and symptomatic, focusing on seizure control with antiepileptic medications and developmental support through early intervention programs. Dietary restriction of carnosine-containing foods (primarily meat) has been attempted in some cases, though the efficacy of this approach remains uncertain. Genetic counseling is recommended for affected families.

Common questions about Carnosinase deficiency