Rett Syndrome: A Genetic Disorder that Primarily Affects Females

Rett syndrome is a rare and severe genetic disorder that normally affects girls, and rarely affects boys. It affects neurological, or brain development and produces symptoms that are very similar to autism. It is estimated that 1 out of every 10,000 to 15,000 girls will develop this disorder.

Symptoms of Rett syndrome vary from person to person. Most commonly, there is a period of normal development, generally from birth to 6 to 18 months of age. After this time, progress slows. In some instances, there are signs present at birth, and no normal developmental period at all. Some develop more mild symptoms than others, even retaining the ability to speak, while others have more severe symptoms and may experience seizures along with other symptoms.

There are four common stages of Rett syndrome.

During the first stage, known as "early onset", many of the signs and symptoms are easily overlooked. This stage normally begins between the ages of 6 and 18 months. One of the first, and often overlooked symptoms is the slowing of head growth. During this stage, babies may exhibit less eye contact with those looking at them and a loss of interest in toys, Loss of muscle tone may be apparent during this stage as well, and there may be delays in things such as sitting up or crawling.

During the second stage, known as "rapid destructive stage", signs of social and language skills begin to deteriorate. This stage normally begins between the ages of 1 and 4 years. At this stage of Rett syndrome, it is common for the affected person to lose the purposeful use of their hands. They tend to habitually wring or rub their hands together as if they are constantly washing their hands, tapping or clapping their hands for no apparent reason is also common. This is also the stage where the affected person develops a severe social anxiety; showing signs of withdrawal and a lack of interest in other people, and stops talking. They may begin to hold their breathe or hyperventilate, scream or begin crying for no apparent reason. Loss of muscle tone makes it difficult for them to initiate movement and gait patterns are unsteady. It is during this stage of Rett syndrome when the slowing of head growth is normally noticed.

The third stage of Rett syndrome, known as the "plateau stage" or "pseudo-stationary stage", normally occurs between the ages of 2 and 10 years, and can last for many years. During this stage, problems with mobility continue, however; do not tend to worsen, and behavioral problems seem to lessen. Children in this stage tend to cry less, are less irritable, and may even show an increase in alertness, attention span and non-verbal communication skills. It is common for those affected to remain in this stage for the majority of their life, however; this is not always the case.

The fourth, and final stage of Rett syndrome, known as the "late motor deterioration stage" can begin anywhere from the ages of 5 to 25. This stage can last for many years, last only a short time, or not become present at all. During this stage of Rett syndrome, there is reduced mobility, muscle weakness and scoliosis present. In general, the ability to understand and communicate do not decline. Repetitive hand movements may decrease. In general, there is typically no further declination of hand skills. Although most people affected by Rett syndrome live into their 40s or 50s, sudden death during deep sleep can occur.

Currently, there is no cure for Rett syndrome. It is caused by mutations in the MECP2 gene which is found on the X chromosome. This particular gene is involved in making a protein that is necessary for normal brain development. Not all cases of Rett syndrome have a typical gene mutation of the MECP2 gene, therefore; it is believed that these children have mutations in a different part of the gene that has not yet been identified.

Girls have two X chromosomes in each cell of their body. Each cell only needs one working copy of the gene, therefore; each cell automatically inactivates one copy of its two X chromosomes. The more cells that have inactivated the X chromosome that carry the mutated MECP2 gene, the less severe the symptoms of Rett syndrome are.

Boys, on the other hand, only have one X chromosome in each cell of their body. Their bodies cannot automatically turn off a copy of the X chromosome because only one copy is present. If there are mutated MECP2 genes in the X chromosome of boys, they are not protected from the effects of the disorder. Most boys with Rett syndrome die before they are born or very early in infancy.

The presence of two X chromosomes in a girl and only one in a boy is the reason why it is extremely rare for Rett syndrome to be present in boys that are living.

Less than one percent of all cases of Rett syndrome are inherited. This means that in less than one percent of all known cases, the parents have passed the disorder on to the child. It is more commonly caused by a mutation in the gene that occurs randomly and without apparent cause. If a mother gives birth to a daughter with Rett syndrome, the chances of those same parents having a second child with the disorder are less than one percent. Genetic testing while pregnant can help determine is the baby will have Rett syndrome.

Rett syndrome is diagnosed based on a girl's patterns of behavior and development. There is specific criteria used to make the diagnosis. Some girls affected with Rett syndrome have symptoms that do not completely fulfill the criteria. In these instances, they are diagnosed as having atypical, or abnormal, Rett syndrome. These cases account for about 15% of all cases of Rett syndrome.

Guidelines for clinical diagnosis of Rett syndrome are divided into three specific types of criteria; essential, supportive and exclusion. When any exclusion criteria is present, it negates a typical Rett syndrome diagnosis.

Essential criteria is criteria that is necessary for diagnosis and includes normal early development until the age of 6 to 18 months, normal head size at birth followed by a slowing in head growth rate between the ages of 3 months and 4 years. In addition, other essential criteria include repetitive hand movements, loss of purposeful hand movement, severe loss of language and speaking ability, unsteady, wide-based and stiff-legged gait or walking on the toes, and the shaking of the torso.

Supportive criteria is criteria that supports the diagnosis, but is not always necessary for diagnosis. These are things that may occur with Rett syndrome, but vary in severity from child to child. These things may not be present in younger children, but may present with age, or not at all. If a child has supportive criteria, but no essential criteria, the child does not have Rett syndrome. Supportive criteria for Rett syndrome includes breathing difficulties, abnormalities in an EEG, seizures, rigidity in the muscles, joint contractures and/or spastic joints that worsens with age, grinding of the teeth, scoliosis, small feet in relation to the child's height, decreased muscle mass and body fat, sleep pattern abnormalities, irritability or agitation, difficulties in chewing and/or swallowing, poor circulation in the lower parts of the body that causes cold and bluish-red or purple colored feet and legs, decrease in mobility with age, and constipation. These things can support a diagnosis of Rett syndrome when they are present with essential criteria, however; without essential criteria present, Rett syndrome is not the diagnosis.

Exclusion criteria are things that can help rule out the diagnosis of Rett syndrome. In general, these things point away from Rett syndrome and a diagnosis of Rett syndrome is not made. Exclusion criteria includes, enlargement of body organs or any other signs of storage disease, retinal disorder or optic atrophy that causes vision loss, microencephaly at birth, a metabolic disorder that is identifiable, an inherited degenerative disorder, an acquired neurological disorder that results from a severe infection or head trauma, any evidence of growth retardation while still in the womb, or any evidence of brain damage acquired after birth. If any of these things are present, Rett syndrome is typically not diagnosed. If a diagnosis of Rett syndrome is made with any of these things present, it is considered to be an atypical case of Rett syndrome.

Treatment of Rett syndrome focuses on treating the symptoms. Currently there is no cure for Rett syndrome. Therapies are often used to help the person affected reach their full potential. Medications can be given to help manage seizures and some movement problems. Those affected with Rett syndrome require assistance and ongoing care for their entire life. The life expectancy of a person with Rett syndrome in 40 to 50 years, some dying much younger and some living to be older. The best chance for those affected with Rett syndrome comes from early diagnosis. For this reason, it is important that you report any behavioral or developmental changes to your child's doctor and keep all well-baby and well-child appointments.

Sources for this article include:

http://www.mayoclinic.com/health/rett-syndrome
http://www.healthnewsflash.com?conditions/rett-syndrome.php
http://www.webmd.com/brain/autism/rett-syndrome
http://www.betterhealth.vic.gov.au