Rett syndrome is a progressive genetic disorder that affects neural development and that occurs almost exclusively in females. Rett syndrome  is characterized by normal growth and development for the first six to 18 months of life, followed by a slowing of development and loss of some acquired motor and speech skills.

Rett syndrome is diagnosed through physical examination and a review of medical history. Genetic testing also can be done to look for mutations commonly associated with the disease.

Physical diagnostic criteria

During the physical examination and medical history review, physicians will look for several criteria to diagnose Rett syndrome. These criteria, or guidelines, fit into three different categories: essential, supportive, and exclusion.

Essential criteria

The essential criteria must be present for the physician to reach a diagnosis of Rett syndrome. They are:

  • Loss of previously acquired hand skills
  • Loss of previously acquired speech and communication skills
  • Repetitive hand movements such as wringing, washing, or clapping movements
  • Abnormal gait such as walking on toes or a wide-stance and stiff-legged walk

Supportive criteria

These often are seen in patients with Rett syndrome, but are not sufficient on their own to diagnose the condition. They include:

  • Grinding teeth (bruxism)
  • Abnormal sleep patterns
  • Abnormal curvature of the spine (scoliosis)
  • Delayed growth
  • Small head size (microcephaly)
  • Small hands and/or feet with poor circulation
  • Breathing problems, including hyperventilation, breath-holding, and swallowing air
  • Abnormal muscle tone such as spasticity, hypotonia, and rigidity
  • Unusual eye movements like intense staring, crossed eyes, or blinking out of unison
  • Inappropriate laughing and screaming spells
  • Reduced response to pain

Exclusion criteria

If any of these criteria are present, then the physician can rule out a diagnosis of Rett syndrome.

  • Brain injury caused by trauma, a neurometabolic disorder (problems in the nervous system related to how the body gets energy from food or uses it), or severe infection
  • Abnormal development during the first six months of life

Genetic testing

Genetic testing through blood samples also can be used to help diagnose Rett syndrome. Most cases of Rett syndrome are caused by a mutation in the MECP2 gene, which encodes for a protein called methyl-CpG binding protein 2. However, mutations in the MECP2 gene also can cause other disorders so physical examination is required for a diagnosis. Other genes that may be associated with Rett syndrome include CDKL5, FOXG1, and WDR5.

Prenatal diagnosis through amniocentesis, which involves testing a sample of the amniotic fluid surrounding a fetus, can be used to identify Rett syndrome before birth.

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