Intellectual disability (ID) is variable. Two third of all patients have mild to moderate ID, while one third has severe ID. Of note, some individuals reportedly have intellectual capacities within the normal range.
Neuromotor delay often precedes ID. Active language development is often more affected than passive language development. Motor delay may result from hypotonia, presenting in about half of all patients. Some patients develop spasticity and contractures.
Most patients have oromotor problems, contributing to articulation difficulties and sometimes feeding difficulties (chewing problems), resulting in failure to thrive.
Recurrent facial features including a high broad forehead, a frontal upsweep, bent and downslanting palpebral fissures, ptosis and/or blepharophimosis, and a bulbous nasal tip. About one third of patients has a single palmar crease. Most patients are relatively macrocephalic.
Behavioral problems (attention deficit (hyperactivity) disorder and aggression) and autistic features are common.
Brain (white matter abnormalities, cerebral atrophy, cerebellar abnormalities), eye (strabismus, hypermetropia), cardiac (mostly atrial septum defect) and urogenital malformations (cryptorchidism, hypospadias), and inguinal hernia can be associated.
Not all individuals with a mutation in the FOXP1 gene have these features. Patients with a 3p microdeletion encompassing FOXP1 generally have more severe intellectual disability and may have hearing loss.