CLS is characterised by a number of features some of which, to a greater or lesser degree of severity, are present in affected individuals, with females likely to be less severely affected. Manifestations include:
- significant learning delay (see entry Learning Disability)
- mild-to-moderate restricted growth (see entry Restricted Growth)
- speech problems (see entry Speech and Language Impairment)
- facial features that may include abnormally prominent brow, unusually thick eyebrows, down slanting palpebral fissures (eyelid folds), hypertelorism (widely-spaced eyes), a broad nose, protruding (nares) nostrils, maxillary hypoplasia (an underdeveloped upper jaw bone) and large ears
- progressive coarsening of the facial features
- 'puffy' hands and feet with tapering digits
- kyphoscoliosis (backward and lateral curvature of the spine; see entry Scoliosis)
- stimulus-induced drop attacks (episodes of interruption to the cerebral (brain) blood flow affecting the balance and causing the individual to fall) affecting ten to 20 per cent of children and adolescents.
Although no clear pattern of behavioural or psychological features relating to CLS has been established, people with the syndrome seem to have a higher incidence of psychiatric difficulties.