People with DS may have some or all of these physical characteristics: a small chin, slanted eyes, poor muscle tone, a flat nasal bridge, a single crease of the palm, and a protruding tongue due to a small mouth and relatively large tongue. Other features include: a flat and wide face, a short neck, excessive joint flexibility, extra space between big toe and second toe, abnormal patterns on the fingertips and short fingers. Short stature is a characteristic feature of DS. Growth retardation of DS individuals starts prenatally. After birth, the growth velocity is most reduced between 6 months to 3 years . Growth charts specific for children with DS are important tools for routine medical follow-up, as well as early identification of pathological causes of growth retardation, and monitoring of growth promoting treatments. Growth charts for DS are available from different countries, for example, Italy, USA, Denmark, Sweden, Portugal, France, UK and Ireland and Saudi Arabia .
Down syndrome or Down's syndrome (DS), also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. It is usually associated with physical growth delays, mild to moderate intellectual disability, and characteristic facial features. The parents of the affected individual are usually genetically normal. The probability increases from less than 0.1% in 20-year-old mothers to 3% in those of age 45 .