GTP Cyclohydrolase I Deficiency

**Semantic type:** Disease or Syndrome

**Definition:** An autosomal recessive condition caused by mutation(s) in the GCH1 gene, encoding GTP cyclohydrolase 1. It is characterized by hyperphenylalaninemia and GTP cyclohydrolase 1-deficient dopa-responsive dystonia.

**Synonyms:** - GTPCH Deficiency