Objective: To present a rare cause of treatable dystonia with onset during adulthood.

Background: L-Dopa-responsive dystonia is an inherited disorder characterized by early-onset dystonia affecting the lower limbs, with diurnal fluctuations and a dramatic response to L-dopa. It is associated with genomic variations in the genes such as GTP cyclohydrolase1(GCH1) and tyrosine hydroxylase, which have been shown to encode enzymes involved in the biosynthesis of dopamine and tetrahydrobiopterine.

Method: A 39-year-old woman presented with a two-year history of head retraction and contraction on her right arm.  Her medical history was unremarkable. She was born to consanguineous parents. On neurologic examination, torticollis, dystonia on her right side and mild parkinsonian signs were noted.

Results: Laboratory findings were normal. A brain MRI scan showed normal findings except for an arachnoid cyst located in the cerebellum. Given her family history, whole exome sequencing (WES) was performed revealing the novel c.284C>T (p.Pro95Leu) variation in the GCH1 gene. The patient’s complaints improved markedly with low-dose L-dopa.

Conclusion: Although L-dopa-responsive dystonias most commonly develop in childhood, they may be encountered at all ages. Therefore, testing for L-dopa response is warranted in all cases with dystonia. Genetic screening with WES should be be incorporated into the diagnostic work-up for dystonia.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/late-onset-dopa-responsive-dystonia-a-case-report/