The syndrome caused by mutations in the MYT1L gene is a multisystem disorder characterized by mild to moderate intellectual disability.
Patients present with motor delay, speech delay and overweight.
In some cases hyperphagia, CNS malformations and behavioural and psychiatric problems, such as aggressive, autistiform, and hyperactive behaviour, stereotypic movements and also sleep disturbance have been observed.
Facial dysmorphisms are minor and include a long chin, broad nasal tip, and upslanting palpebral fissures.