The analysis of etiologies suggested a predominant association of chorea with a subset of genes or CNV involved in post-synaptic signaling (e.g., GNAO1, GNB1, FOXG1, MEF2C, CLN2, MeCP2 duplication) and a high quote of the pathogenic gene or chromosomal variants associated with neurodegenerative and metabolic diseases among patients presenting with myoclonus and parkinsonism. The gene discussed is MECP2; the disease is Parkinsonism.