Carnosinemia

An inherited metabolic disorder characterized by severe mental defect and myoclonic seizures.

(Serum-) Carnosinase Deficiency; Beta-Alanine-Pyruvate Aminotransferase; Hyper-Beta Carnosinemia

Fewer than 10 cases have been described. Autosomal recessive transmission with the mutation located on 18q21.3. Parental consanguinity has been described in some of the cases.

Progressive neurologic disorder with variable phenotype associated with severe mental retardation, myoclonic seizures, tremor, and hypotonia caused by a defect in carnosinase activity. Central nervous system findings at autopsy may include severe axonal degeneration, loss of Purkinje fibers, and neuraxonal spheroids in the gray matter as a result of demyelinization and reactive fibrosis. Carnosine, a dipeptide of histidine and alanine, is found in significant concentrations in meat. A strictly meat-free diet can result in amelioration of the symptoms, but does not provide a cure. Deficiency of carnosinase results in high serum and urine levels of carnosine.

Anesthesia in these patients has not been described. Patient cooperation may be limited secondary to mental retardation. Sedative and anxiolytic premedication and the presence of the primary caregiver during induction of anesthesia may be helpful. Consider interaction between anesthetic drugs and antiepileptic treatment and avoid drugs that reduce the seizure threshold.