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Sotos syndrome

Also known as: Cerebral Gigantism in Childhood

Background

In this rare syndrome, babies are generally significantly larger and heavier than average caused by excessive prenatal (before birth) and early post-natal (after birth) growth.

Credits

Last updated February 2015 by Dr R Stanhope, Consultant Paediatric Endocrinologist, The Portland Hospital, London, UK.

What are the symptoms?

Characteristics include macrocephaly (large head) with accelerated bone development. Children may have delayed development and language problems. In addition, the faces of children with Sotos syndrome may appear similar, including widely spaced eyes, a prominent jaw and high-arched palate (roof of the mouth). Some children will have normal intelligence; however, some may have a mild form of learning disability. Children with Sotos syndrome may be clumsy or ataxic (unsteady).

Growth rate of children with Sotos syndrome usually slows at four to five years of age. Adults are usually a similar height to adults without the syndrome. Weaver syndrome is a condition characterised by accelerated growth, mild hypotonia (low muscle tone), loose skin, thin hair and camptodactyly (permanent immobility of a flexed finger joint). In the first years of life, Sotos syndrome may be misdiagnosed as Weaver syndrome.

Some people with Sotos syndrome also have behavioural problems. Frequent behavioural issues include attention deficit hyperactivity disorder (ADHD), phobias, obsessions and compulsions, tantrums and impulsive behaviours.

What are the causes?

Mutations in the NSD1 gene cause Sotos syndrome. The NSD1 gene provides instructions for making a protein that is involved in normal growth and development. It is unclear how a reduced amount of this protein during development leads to learning disabilities, overgrowth and the other features of Sotos syndrome.

How is it diagnosed?

Sotos syndrome may be suspected during pregnancy or noted shortly after birth, due to overgrowth. A molecular test (testing the DNA) in the NDS1 gene may confirm the diagnosis. For some children, only a clinical diagnosis will be given.

How is it treated?

Sotos syndrome is managed by providing support to children affected by the condition in some areas of their lives. There is no cure for the condition at the moment. It is not a life-threatening condition and those affected may have a normal life expectancy. The initial abnormalities of Sotos syndrome usually resolve as the growth rate becomes normal after the first few years of life.

Developmental delays may improve in the school-age years, and adults with Sotos syndrome are likely to be within the normal range for intellectual ability and height. However, coordination problems may persist into adulthood. Special educational support may be required.

Inheritance patterns and prenatal diagnosis

Inheritance patterns 
Most cases are sporadic mutations and occur by chance in a previously non-affected family. A few families have been described with more than one affected family member and this has confirmed that the inheritance for any children of somebody with Sotos syndrome is autosomal dominant. Weaver syndrome probably has some pattern of inheritance, though this has not been fully determined. Genetic counselling is available for affected families.

Prenatal diagnosis
Macrocephaly, large hands, long arms and excessive growth are detectable using ultrasound scanning.

Is there support?

Information and support in the UK for Sotos syndrome is provided by the Child Growth Foundation (see entry  Restricted Growth).