Patients may present with these features:
- Craniosynostosis: premature fusion of the sutures of the skull
- Skeletal muscle hypotonia: decreased muscle tone
- Intellectual disability
- Proptosis: protruding eyeballs
- Dolichocephaly: long head
- Hypertelorism: widely spaced eyes
- Myopia: near-sightedness
- High arched and narrow palate
- Downslanting palpebral fissures: downward slanting the eye line
- Retrognathia: a small or retracted lower jaw
- Arachnodactyly: extreme long and slender fingers
- Camptodactyly: permanent flexion of one or more finger joints
- Scoliosis: abnormal curvature of the spine
- Pectus deformity: inward or outward malformation of the chest bone
- Joint hypermobility
- Joint contractures
- Mitral valve prolapse: bulging of the mitral valve leaflets into the left atrium
- Aortic dilatation: widening of the aorta
Patients with a genetic variant affecting amino acid 180 (Thr) display a milder morphological phenotype with a marfanoid habitus and no intellectual disability.