Dopa-responsive dystonia (DRD) due to tyrosine hydroxylase deficiency.
Incidence
The condition is transmitted as autosomal recessive but the true incidence is unknown.
Clinical Characteristics
This condition presents with parkinsonian symptoms since infancy through adolescence. Dystonia with diurnal variation is present. Central nervous system symptoms such as hypokinesia, bradykinesia, trunkal hypotonia can be present. Bilateral ptosis and drooling also may be present as well as microcephaly. Some cases mimic spastic diplegia cerebral palsy with deep tendon reflexes and pseudo-Babinski sign. Special laboratory testing include decrease levels of homovanillic acid (HVA) in the spinal fluid. Levels of 5HIAA in CSF are normal as well as neopterine and biopterine in the spinal fluid. This is in contrast with the GTPCH deficiency where neopterine in CSF is decreased Diagnosis is made by measuring the enzyme in lymphoblasts or fibroblasts. Imaging studies are normal. The diagnosis of dopamine responsive dystonia should be considered in all cases of dystonia, regardless of clinical features, including cases of apparent dystonic cerebral palsy as the onset may be as early as one year of age and a therapeutical trial is indicated when any doubt exists. Treatment is similar to dopa-responsive dystonia due to GTPCH deficiency. Treatment with L-dopa often combined with inhibitor of peripheral catabolism (carbidopa) is used in a small dose of 50-250 mg. per day and can be effective from the first one or two days of treatment.
Precipitants
no
Provocation Tests
no
Diagnostic Procedures
EB-F. Diagnosis is made by measuring the enzyme in lymphoblasts or fibroblasts. Special laboratory testing include decrease levels of homovanillic acid (HVA) in the spinal fluid. Levels of 5HIAA in CSF are normal as well as neopterine and biopterine in the spinal fluid. This is in contrast with the GTPCH deficiency where neopterine in CSF is decreased