Criteria for the clinical diagnosis of Rett syndrome, according to Clarke50
| Necessary criteria | Supportive criteria |
| Normal prenatal and perinatal development | Seizures |
| Loss of acquired skills such as communication and speech | Abnormal EEG |
| Normal head circumference at birth with acquired microcephaly | Apnoea |
| Marked developmental delay | Hyperventilation |
| Loss of hand skills | Breathing dysfunction with breath holding |
| Autistic features | Scoliosis |
| Gait apraxia | Growth retardation |
| Stereotypic hand movements | Cold feet |
| Spasticity with muscle wasting |