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How do health care providers diagnose Rett syndrome?

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Blood Test

Genetic evaluation of a blood sample can identify whether a child has one of the known mutations that cause Rett syndrome.1 Even if a child has a mutation of the Methylcytosine-binding protein 2 (MECP2) gene (which also occurs in other conditions), the symptoms of Rett syndrome may not always be present, so health care providers also need to evaluate the child's symptoms to confirm a diagnosis.1

Clinical Symptoms

A child must meet the following five necessary criteria to be diagnosed with classic Rett syndrome:2,3

Main Diagnostic Criteria

  • A pattern of development, regression, then recovery or stabilization
  • Partial or complete loss of purposeful hand skills such as grasping with fingers, reaching for things, or touching things on purpose
  • Partial or complete loss of spoken language
  • Repetitive hand movements, such as wringing the hands, washing, squeezing, clapping, or rubbing
  • Gait abnormalities, including walking on toes or with an unsteady, wide-based, stiff-legged gait

A slowing of head growth between 3 months and 4 years of age, leading to acquired microcephaly (pronounced mahy-kroh-SEF-uh-lee), is also characteristic of Rett syndrome and calls for a diagnosis to be considered.3,4

For additional information and a listing of the supportive criteria, visit the International Rett Syndrome Foundation webpage External Web Site Policy .

Health care providers will also consider whether any of the following conditions are present. The presence of any of the symptoms below would rule out a Rett syndrome diagnosis.

Atypical Rett Syndrome

Genetic mutations causing some atypical variants of Rett syndrome have been identified. After a blood test to confirm a child's genetic makeup, a health care provider may diagnose the child with atypical Rett syndrome if the child demonstrates development, followed by regression and then recovery or stabilization. In addition, the health care provider will confirm at least two of the other four main criteria, and five of the 11 supportive criteria before making a diagnosis.2

Other Possible Diagnoses

Sometimes Rett syndrome is misdiagnosed as regressive autism, cerebral palsy, or nonspecific developmental delays.1

For some males, the features of Rett syndrome occur with another genetic condition called Klinefelter syndrome, in which a boy has two X chromosomes and one Y chromosome. This means that the boy may have one mutated MECP2 gene and one normal MECP2 gene, reducing the effects of the mutated gene.


  1. International Rett Syndrome Foundation. (2008). About Rett syndrome. Retrieved May 10, 2012, from http://www.rettsyndrome.org/understanding-rett-syndrome/about-rett-syndrome External Web Site Policy [top]
  2. Neul, J. L., Kaufmann, W. E., Glaze, D. G., Christodoulou, J., Clarke, A. J., Bahi-Buisson, N., et al. (2010). Rett syndrome: Revised diagnostic criteria and nomenclature. Annals of Neurology, December;68(6), 944–950. Retrieved June 23, 2012, from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3058521 See diagnostic table at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3058521/table/T1 [top]
  3. International Rett Syndrome Foundation. (2008). About Rett Syndrome: Testing & Diagnosis. Retrieved June 23, 2012, from http://www.rettsyndrome.org/understanding-rett-syndrome/about-rett-syndrome/testing-diagnosis External Web Site Policy [top]
  4. Hagberg, B., Hanefeld, F., Percy, A., & Skjeldal, O. (2002). An update on clinically applicable diagnostic criteria in Rett syndrome. Comments to Rett Syndrome Clinical Criteria Consensus Panel Satellite to European Pediatric Neurology Society Meeting, Germany 2001. European Journal of Pediatric Neurology, 6, 293–297. [top]

Last Updated Date: 01/28/2014
Last Reviewed Date: 01/14/2014
Vision National Institutes of Health Home BOND National Institues of Health Home Home Storz Lab: Section on Environmental Gene Regulation Home Machner Lab: Unit on Microbial Pathogenesis Home Division of Intramural Population Health Research Home Bonifacino Lab: Section on Intracellular Protein Trafficking Home Lilly Lab: Section on Gamete Development Home Lippincott-Schwartz Lab: Section on Organelle Biology