Sotos syndrome is a rare genetic disorder characterized by excessive physical growth during the first years of life.

The disorder may be accompanied by autism,[1] mild intellectual disability, delayed motor, cognitive, and social development, hypotonia (low muscle tone), and speech impairments.

Adult height is usually in the normal range, although Broc Brown has the condition and was named the world's tallest teenager; as of late 2016, he was 2.34 m (7 ft 8 in) tall and still growing.

Additionally, weak muscle tone (hypotonia) may delay other aspects of early development, particularly motor skills such as sitting and crawling.

[citation needed] Other signs include scoliosis, seizures, heart or kidney defects, hearing loss, and problems with vision.

[8][9] The NSD1 gene provides instructions for making a protein (histone-lysine N-methyltransferase) that is expressed mainly in the brain, kidney, muscle, spleen, thymus, and lung.

The specific function of this protein is not yet known but studies show that it is involved in histone modification, which affects transcription of other genes.

[10] It is unclear how a reduced amount of this protein during development leads to learning disabilities, overgrowth, and the other features of Sotos syndrome.

[11] The clinical evaluation begins with a physician conducting a thorough history and physical examination, focusing on signs of excessive growth along with other previously mentioned symptoms.

Developmental delays may improve in the school-age years; however, coordination problems may persist into adulthood, along with any learning disabilities and/or other physical or mental issues.