Rett syndrome is a progressive genetic disorder that affects neural development and occurs almost exclusively in females. This syndrome is characterized by normal growth and development for the first 6 to 18 months of life, followed by a slowing of development and loss of some acquired motor and speech skills.
Genetic testing can be done to look for mutations commonly associated with the disease. However, as those mutations have been found in people lacking the characteristic clinical features of Rett, physical examination and a review of medical history also are performed.
Physical diagnostic criteria
During the physical examination and medical history review, physicians will look for several criteria, or guidelines, to diagnose Rett syndrome. These criteria fit into three categories: essential, supportive, and exclusion.
Essential criteria
The essential criteria must be present for the physician to reach a diagnosis of Rett syndrome. These include:
- Loss of acquired purposeful hand skills
- Impairment of acquired speech and communication skills
- Repetitive hand movements, such as wringing, rubbing, or clapping movements
- Gait abnormalities, such as walking on toes or a wide-stance and stiff-legged walk
Supportive criteria
These often are seen in people with Rett syndrome, but are not sufficient on their own to diagnose the condition. They include:
- Bruxism (teeth grinding)
- Irregular sleep patterns
- Scoliosis, which refers to a sideways curvature of the spine
- Delayed growth
- Small hands and/or feet with poor circulation
- Breathing problems, including hyperventilation (or fast breathing), breath-holding, and swallowing air
- Spasticity (muscle stiffness or spasms), low muscle tone, and muscle rigidity
- Unusual eye movements, as intense staring, crossed eyes, or blinking
- Inappropriate laughing and screaming spells
- Reduced response to pain
Exclusion criteria
Because Rett syndrome is rare, other conditions may need to be excluded. If any of these criteria are present, the physician can rule out a diagnosis of Rett syndrome:
- Brain damage caused by trauma or acquired after birth
- Neurometabolic disorder (problems in the nervous system related to how the body gets energy from food or uses it)
- Neurological issues caused by severe infection
- Unusual development during the first six months of life
Other conditions may be causing some of the same symptoms as Rett syndrome. Some of them are:
- Autism
- Cerebral palsy (a group of disorders that affect movement, posture, and balance)
- Neurodegenerative disorders
- Brain damage around or after birth
Genetic testing
Genetic testing through a simple blood sample can be used to confirm the diagnosis of Rett syndrome.
Most cases of Rett syndrome are caused by a mutation in the MECP2 gene, which provides instructions for making a protein of the same name. However, mutations in the MECP2 gene also can cause other disorders, so physical examination is required for a diagnosis.
Mutations in MECP2 typically occur de novo, meaning they are not inherited. Prenatal diagnosis through amniocentesis, which involves testing a sample of the amniotic fluid surrounding a fetus, can be used to identify a Rett-causing mutation before birth.
A genetic test also can be used to detect mutations in other genes, including CDKL5 and FOXG1. These genes have been linked to atypical types of the disease, for which symptoms do not meet all the diagnostic criteria for Rett syndrome.
Other tests
Other tests may include MRI or CT scans, hearing and eye exams, and an electroencephalogram — a noninvasive test that records the electrical activity in the brain.
Last updated: April 29, 2021
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