Boys can also suffer from Rett syndrome. The main causative gene, MECP2, is located on the X chromosome (Xq28), and most of the mutated genes come from the paternal X chromosome, so the majority of patients are girls. However, there are cases in which boys are affected. The possibility of Rett syndrome is considered when boys suffer from symptoms associated with the disease, such as decreased intelligence, speech, hand function, and motor skills.