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.