Two siblings from a Hong Kong Chinese family are diagnosed to have heterozygous mutation in tyrosine hydroxylase gene-a novel mutation R169X and the common Dutch mutation R233H. Presented with developmental delay and dystonia before 6 months of age, both had hyperprolactinemia with persistent galactorrhea present in the elder brother since birth. Serum prolactin level is a good screening test for those suspected of underlying neurotransmitter diseases. To our knowledge, this is the first Chinese family diagnosed with such condition. Clinicians must be aware of this rare disease especially in those unexplained 'cerebral palsy' like children.