Sotos Syndrome - A Rare Genetic Disorder
Synopsis: Sotos syndrome is a variable genetic disorder characterized by excessive growth before and after the person is born. Sotos syndrome is a form of variable genetic disorder that is characterized by excessive growth both before and after the person is born.
Main DigestSotos syndrome is a form of variable genetic disorder that is characterized by excessive growth both before and after the person is born.
One of the major features of the syndrome is a specific facial appearance that includes a prominent forehead, facial flushing, prominent, narrow jaw, down-slanting eyelid folds, and a head shape resembling an inverted pear. The person's height and head circumference are greater than average for the majority of children affected by the syndrome.
Children with Sotos syndrome often experience developmental delays that may include motor and language delays, as well as mental retardation ranging from mild to severe. Additional problems associated with the syndrome include scoliosis, jaundice in newborns, crossed eyes, seizures, congenital heart defects, conductive hearing loss, behavioral problems, and kidney abnormalities. People affected by Sotos syndrome may also have a somewhat higher risk of developing particular types of tumors. Sotos syndrome is caused by a mutation in the NSD1 gene.
The syndrome causes physical overgrowth during the first years of a child's life. Children with the syndrome are many times taller and have larger heads than other children the same age. Due to the distinctive shape and size of their heads, Sotos syndrome is sometimes referred to as, 'cerebral gigantism.' There is a certain amount of irony in this name because the syndrome is often accompanied by motor, cognitive, and social delays. Children affected by the syndrome experience low muscle tone and speech that is markedly impaired.
While children who appear older while behaving younger may be at risk for strained peer and family relationships or problems in school, late childhood often finds the gap beginning to close. The child's muscle tone improves and along with it, better speech. For many people, Sotos syndrome largely changes their developmental timing. Despite early trends, adults with Sotos syndrome might be within the average range of both height and intellect.
There are many genetic conditions that are plain at the time a child is born. A diagnosis can be reached through specialized laboratory testing. Sotos syndrome is not one of these conditions; a diagnosis is often made months or even years after the child is born after a slow process of questioning whether anything is wrong and listening to rather vague reassurances. Parents may hear, 'doom and gloom,' projections or cherish hopeful signs before receiving a diagnosis.
Features of Sotos Syndrome
There are many features associated with Sotos syndrome. These features include the following:
- Heart defects
- Abnormal EEG
- Low muscle tone
- Thyroid disorders
- High arched palate
- Glucose intolerance
- Advanced bone age
- Prominent forehead
- Learning disabilities
- Developmental delay
- Autonomic dysfunction
- Nystagmus, strabismus
- Behavioral disturbance
- Poor fine motor control
- Apparent hypertelorism
- Prominent, pointed chin
- I.Q. in the normal range
- Constipation, megacolon
- Expressive language delay
- Disclocated hips or club feet
- Excessive growth in childhood
- Increased birth length and weight
- Macrocrania without megalencephaly
- Frequent upper respiratory infections
- Premature tooth eruption, soft enamel
- Rosy coloring over the cheeks and nose
- Disproportionately large hands and feet
- Persistent feeding difficulties and / or reflux
- Characteristic structural changes in the brain on MRI
- Down-slanting palpebral fissures or "antimongoloid slant"
Treatment for Sotos syndrome is based upon the symptoms the person is experiencing; there is no standard course of treatment for it. The syndrome itself is not life-threatening and people with it can have an average life expectancy. The initial abnormalities of Sotos syndrome commonly resolve as the person's growth rate becomes average after the first few years of their life. Developmental delays can improve in the person's school-age years. Adults with Sotos syndrome are likely to be within the average range for both height and intellect. Coordination issues; however, may continue into adulthood.
Newborns with Sotos syndrome have foreheads described as disproportionately large and rounded that might be pinched at the temples. Their eyes have a slight downward slant at the corners and due to a narrowing of the temples, appear wide-set. The newborns have a prominent, pointed jaw adding to the appearance of a long and narrow face and skull. The roof of their mouth may be high. The newborn's feet and hands can appear large. Low muscle tone causes a floppy appearance, and poor sucking is pronounced; approximately one-third of children with the syndrome must be fed through a gastrointestinal tube. About forty-percent spend some time under, 'bili lights,' because of jaundice.
Feeding continues to be an issue for a number of infants with Sotos syndrome; head control develops late, and poor muscle tone impairs rolling, sitting, crawling, standing, and walking. Activities requiring fine motor control such as playing with objects, grasping, and facial expressions are also delayed. The child's head may grow at an alarming rate.
Physical and occupational therapies play an important role in assisting a child with Sotos syndrome. Through these forms of therapy, the child has the ability to practice balance, movement, and hand skills with the goal of avoiding bad habits related to posture and gait. Additional strategies for effective movement may give the child more mobility and encourage self-help skills. Provision of opportunities for success and mastery promotes the child's self-esteem.
Sotos Syndrome Genes and Heredity
The year 2002 found a group of Japanese scientists linking Sotos syndrome to mutations in a gene called, 'NSD1,' or Nuclear SET domain 1. The gene is on the long arm of chromosome 5 and was missing or altered in a number of Japanese children with classic Sotos. Studies performed in other parts of the world confirmed the relationship.
Dr. Trevor Cole and his cohorts in the United Kingdom tested hundreds of people and family members in studies of overgrowth syndromes. They discovered a number of things that include:
- Ninety-percent of people who carried a diagnosis of Sotos by 'strict criteria" had NSD1 mutations.
- About ten-percent of people called "Possible Sotos" or "Sotos-like" had NSD1 mutations. Almost without exception these patient had the classic facial appearance and large head but were shorter than expected for Sotos, or did not have advanced bone age.
- None of the people who did not have the facial features of Sotos had NSD1 mutations.
- The only parents who had NSD1 mutations also had physical features of Sotos syndrome.
- NSD1 is not involved in other known genetic overgrowth conditions, such as Beckwith Wiedemann syndrome and Weaver syndrome.
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