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.
Willi SM, Zhang Y, Hill JB, et al: A deletion in the long arm of
chromosome 18 in a child with serum carnosinase deficiency. Pediatr Res
Wisniewski K, Fleisher L, Rassin D, et al: Neurological disease in a child
with carnosinase deficiency. Neuropediatrics