Dopa-responsive dystonia patient response before and after levodopa treatment

Dopa-responsive dystonia (DRD), also known as Segawa syndrome, is a
phenotypically and genetically heterogeneous group of neurological
disorders that typically presents as early-onset lower limb dystonia with
diurnal fluctuation and exhibits a marked, persistent response to
levodopa. Heterozygous loss-of-function mutations in the guanosine
triphosphate cyclohydrolase 1 (GCH1) are the most common cause of DRD. In
addition to the classic form of the disease, there have been a number of
studies addressing atypical clinical features of GCH1related-DRD with
variable age of onset. This report describes a mid-30-year-old Japanese
male patient with a 10-year history of focal upper limb dystonia that
initially emerged as task-specific, guitarist’s cramp. The dystonic
symptoms responded very well to levodopa treatment, and genetic analysis
identified a novel heterozygous mutation in the C-terminal catalytic
domain of GCH1. Insufficient recognition of this treatable condition often
leads to misdiagnosis, which causes delays in the patient receiving
adequate dopamine replenishing therapy. A diagnostic trial with levodopa
should be considered in all patients with relatively young-onset dystonia,
whether they have classic features of DRD or not.