Guanine triphosphate (GTP)–cyclohydrolase 1 (GCH1)–deficient dopa-responsive dystonia is caused by GCH1 gene mutation. Two children presenting with frequent daily falling are reported with GCH1 gene mutations with persistent response to low-dose levodopa/carbidopa. Typical and atypical clinical features associated with GCH1 mutations are also reviewed.
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