Definition of Rett Syndrome
Rett syndrome (also known as Rett disorder) is a relatively rare, discrete, but progressive neurological disorder that affects brain development and results in mental and physical disability.
The syndrome is mainly noticeable in children between the ages of 6 to 18 months when they start to miss developmental milestones or lose abilities they had gained. Rett syndrome occurs almost exclusively in girls but can also affect boys, though even more rarely (National Institute of Neurological Disorders & Stroke, 2020; National Health Service, 2019; Percy, 2008; & Sulkes, 2020).
Types of Rett Syndrome
Rett syndrome is classified into two main types i.e., ‘classic’ and ‘atypical’ and this classification is mainly based on the type of symptoms or the particular gene mutation that caused the syndrome.
Classic Rett syndrome – this is characterized by four main progressive phases:
- Early Onset Phase – this is when the syndrome takes root at a subtle pace that in some instances, parent and caregivers do not notice at first. However, this is the phase when the affected child’s developmental milestones start to stall or sometimes completely stop.
- Rapid Destructive Phase – this is the phase where the affected child loses skills, with hand movement and speech skills being the first to be lost. Parents and/or caregivers notice that the child has challenges with hand movements such as clasping, squeezing, clapping and tapping. In some instances, the affected child may also have breathing problems.
- Plateau Phase – during this phase the affected child may seem to improve in some areas, however, this is the time when seizures and movement challenges are also commonly exhibited. It is notable that majority of those affected spend most of their lives in this phase.
- Late Motor Deterioration Phase – this is the phase characterized by stiffness or sometimes loss of muscle tone. In some instances, those affected may become immobile. Additionally, Scoliosis, which is the an abnormal curvature of the spine, may be present and even become severe enough to require bracing or surgery.
Atypical Rett syndrome – there are five main forms of atypical Rett syndrome that have been identified so far:
- Congenital Rett syndrome (also known as the Rolando Variant) – this is the most severe of all forms of atypical Rett syndrome characterized with loss of muscle tone and severe delays in development, especially within the first three months.
- Early-onset Seizure Rett-Syndrome (also known as the Hanefeld Variant) – this form is characterized by seizures that usually start before six months of age.
- Late Childhood Regression Rett syndrome – a child affected by this form of Rett syndrome would have normal head circumference but show signs of gradual late childhood loss of some skills such as language and motor skills.
- Forme Fruste Rett syndrome – this form of Rett syndrome is a milder variant characterized by symptoms in early childhood. Those affected may not exhibit all Rett syndrome symptoms and progression of the variant is slower.
- Preserved-Speech Rett syndrome (also known as the Zappella Variant) – the differentiating factor in this form of Rett syndrome is that although most symptoms of the syndrome manifest, they are milder and those affected regain some motor and language skills later.
(National Institute of Neurological Disorders & Stroke, 2020; National Health Service, 2019; Percy, 2008; & Sulkes, 2020)
Causes of Rett Syndrome
Nearly all Rett syndrome cases are caused by a mutation (a change in the DNA) on the X chromosome and specifically in the MECP2 gene. This is the gene that has instructions for the production of a protein (MeCP2) that is critical for brain development, hence any abnormality in the gene incapacitates the effective working of the brain nerve cells leading to slow or missed developmental milestones in affected children.
However, it is important to note that Rett syndrome can also be caused by partial gene deletions, mutations in other genes (such as CDKL5 and FOXG1 genes and others not yet identified) consequently affecting brain development in the affected child with atypical Rett syndrome (National Institute of Neurological Disorders & Stroke, 2020; National Health Service, 2019; Percy, 2008; & Sulkes, 2020).
Symptoms of Rett Syndrome
The progression of Rett syndrome, time of onset and symptom severity often vary from one child to another. Before profound symptoms show, the affected child may appear to progress normally in their growth and development. However, oftentimes, there could be discrete or subtle abnormalities in early childhood including feeding difficulty, loss of muscle tone or challenges with limb movement. Profound symptoms include:
- Slow growth, especially when brain growth slows after birth and the affected child exhibits smaller than normal head size (microcephaly)
- Loss of normal movement and coordination, notable by reduced hand control and a decreasing ability to crawl or walk normally.
- Loss of communication ability characterized by loss of speech and ability to make eye contact.
- Abnormal hand movements manifest by varying repetitive, purposeless hand movements.
- Unusual eye movements including intense blinking, staring, blinking, crossed eyes or a child closing one eye at a time.
- Breathing problems that include abnormally rapid breathing (also known as hyperventilation), shallow or periodic breathing while sleeping, breath-holding etc.
- Seizures (sometimes multiple seizures) that occur in a majority of those affected by this syndrome.
- Abnormal curvature of the spine (scoliosis) often between 8 and 11 years of age and which intensifies with age.
- Other notable symptoms of Rett syndrome may include teeth grinding, challenges chewing and swallowing or problematic bowel function among other symptoms.
(National Institute of Neurological Disorders & Stroke, 2020; National Health Service, 2019; Percy, 2008; & Sulkes, 2020).
National Institute of Neurological Disorders and Stroke. (2020). Rett Syndrome Fact Sheet [Fact sheet].
National Health Service. (2019, October). Rett syndrome. NHS.
Percy, A.K. (2008) Rett Syndrome: Recent Research Progress, Journal of Child Neurology, 23(5), 543-9.
Sulkes, S, B. (2020). Rett Syndrome. Merck Sharp & Dohme Corp (MSD) Manual.