Home > About Rett Syndrome > Symptoms and Diagnosis

Symptoms and Diagnosis

The discovery of the MECP2 gene has made possible the development of a blood test for RTT. The diagnosis of the disorder, however, is still based on symptoms and clinical history.

At this time, approximately 85% of all patients diagnosed with RTT also test positive for an MECP2 mutation. This does not mean that the remaining 15% do not have RTT. Although testing positive for a mutation confirms the diagnosis it is not required. It is possible that mutations exist in an area of MECP2 that has not yet been sequenced, or perhaps other genes contribute to RTT.

The criteria below are used for making a clinical diagnosis of RTT. Please keep in mind that RTT is a spectrum disorder. Not all the symptoms are seen in every patient and the severity of a symptom may vary widely from patient to patient.

Diagnostic Criteria

  • Period of apparent normal development until 6-18 months (some girls have an earlier onset of RTT symptoms and therefore have no normal period of development).


  • Normal head circumference at birth followed by slowing of the rate of head growth (there is a subset of girls whose rate of head growth does not decelerate).


  • Loss of verbal language.


  • Purposeful hand use is replaced by stereotypical hand movements (these can include a multitude of hand movements, some girls have movements unique to them or none at all).


  • If able to walk the gait is usually wide-based and stiff legged.


  • Shakiness of torso and/or limbs, especially when upset.

Supportive Criteria

  • Breathing pattern irregularities which include hyperventilation, breath holding, apnea, air swallowing


  • EEG abnormalities


  • Seizures


  • Scoliosis


  • Teeth grinding


  • Gastrointestinal issues which may include reflux, constipation, poor nutrient absorption


  • Growth retardation and decreased body fat and muscle mass


  • Biting/Chewing/Swallowing difficulties


  • Poor circulation to legs and feet


  • Decreased mobility with age


  • Muscle rigidity/spasticity/joint contractures


  • Small feet


  • Abnormal sleep patterns


  • Irritability and agitation