Tyrosine hydroxylase deficiency: a treatable disorder of brain catecholamine biosynthesis.

Tyrosine hydroxylase deficiency is an autosomal recessive disorder resulting from cerebral catecholamine deficiency. Tyrosine hydroxylase deficiency has been reported in fewer than 40 patients worldwide. To recapitulate all available evidence on clinical phenotypes and rational diagnostic and therapeutic approaches for this devastating, but treatable, neurometabolic disorder, we studied 36 patients with tyrosine hydroxylase deficiency and reviewed the literature. Based on the presenting neurological features, tyrosine hydroxylase deficiency can be divided in two phenotypes: an infantile onset, progressive, hypokinetic-rigid syndrome with dystonia (type A), and a complex encephalopathy with neonatal onset (type B). Decreased cerebrospinal fluid concentrations of homovanillic acid and 3-methoxy-4-hydroxyphenylethylene glycol, with normal 5-hydroxyindoleacetic acid cerebrospinal fluid concentrations, are the biochemical hallmark of tyrosine hydroxylase deficiency. The homovanillic acid concentrations and homovanillic acid/5-hydroxyindoleacetic acid ratio in cerebrospinal fluid correlate with the severity of the phenotype. Tyrosine hydroxylase deficiency is almost exclusively caused by missense mutations in the TH gene and its promoter region, suggesting that mutations with more deleterious effects on the protein are incompatible with life. Genotype-phenotype correlations do not exist for the common c.698G>A and c.707T>C mutations. Carriership of at least one promotor mutation, however, apparently predicts type A tyrosine hydroxylase deficiency. Most patients with tyrosine hydroxylase deficiency can be successfully treated with l-dopa.

Mutations in the cyclic adenosine monophosphate response element of the tyrosine hydroxylase gene.

Tyrosine hydroxylase (TH) deficiency (OMIM 191290) is one cause of early-onset dopa-responsive dystonia. We describe seven cases from five unrelated families with dopa-responsive dystonia and low homovanillic acid in cerebrospinal fluid who were suspected to suffer from TH deficiency. Analysis of part of the TH promotor showed five homozygous and two heterozygous mutations in the highly conserved cyclic adenosine monophosphate response element. Our data suggest that, if no mutations are found in the coding regions of the gene in patients strongly suspected of TH deficiency, the search for pathogenic mutations should be extended to regulatory promotor elements.

Tyrosine hydroxylase deficiency causes progressive encephalopathy and dopa-nonresponsive dystonia.

Tyrosine hydroxylase (TH) is the key enzyme in the biosynthesis of the catecholamines dopamine, epinephrine, and norepinephrine. Recessively inherited deficiency of TH was recently identified and incorporated into recent concepts of genetic dystonias as the cause of recessive Dopa-responsive dystonia or Segawa's syndrome in analogy to dominantly inherited GTP cyclohydrolase I deficiency. We report four patients with TH deficiency and two with GTP cyclohydrolase I deficiency. Patients with TH deficiency suffer from progressive infantile encephalopathy dominated by motor retardation similar to a primary neuromuscular disorder, fluctuating extrapyramidal, and ocular and vegetative symptoms. Intellectual functions are mostly compromised. Prenatally disturbed brain development and postnatal growth failure were observed. Treatment with levodopa ameliorates but usually does not normalize symptoms. Compared with patients with dominantly inherited GTP cyclohydrolase I deficiency, catecholaminergic neurotransmission is severely and constantly impaired in TH deficiency. In most patients, this results not in predominating dystonia, a largely nondegenerative condition, but in a progressive often lethal neurometabolic disorder, which can be improved but not cured by L-dopa. Investigations of neurotransmitter defects by specific cerebrospinal fluid determinations should be included in the diagnostic evaluation of children with progressive infantile encephalopathy.

Tyrosine hydroxylase deficiency: clinical manifestations of catecholamine insufficiency in infancy.

Inborn errors of catecholamine biosynthesis are rare but of great interest as they are genetic disorders, and in some, treatment may completely reverse severe neurological abnormalities. They also provide insights into the action of the biogenic amines in the developing brain. We describe the clinical course of an infant with tyrosine hydroxylase (TOH) deficiency over a 30-month period. The parents are consanguineous, and genetic analysis revealed the infant to be homozygous for the common G698A mutation in the TOH gene. TOH deficiency can be seen as a model of pure catecholamine deficiency. Experimental evidence, reports of other disorders of biogenic amines, and our experience with this infant suggest that the symptoms of catecholamine deficiency in infancy can be broadly subdivided. Signs of dopamine deficiency include tremor, hypersensitivity to levadopa (L-dopa) therapy, oculogyric crises, akinesia, rigidity, and dystonia. Manifestations of norepinephrine deficiency include ptosis, miosis, profuse oropharyngeal secretions, and postural hypotension. Hypersensitivity to L-dopa was a particular management problem in this infant.