The remaining 5% of Down syndrome cases are due to conditions called mosaicism and translocation. Mosaic Down syndrome results when some cells in the body are normal while others have Trisomy 21. Robertsonian translocation occurs when part of chromosome 21 breaks off during cell division and attaches to another chromosome (usually chromosome 14). The presence of this extra part of chromosome 21 causes Down some syndrome characteristics. Although a person with a translocation may appear physically normal, he or she has a greater risk of producing a child with an extra 21st chromosome. Individuals with Down syndrome often have distinct physical characteristics, unique health issues, and variability in cognitive development. Physical characteristics include:
Eyes that have an upward slant, oblique fissures, epicanthic skin folds on the inner corner, and white spots on the iris
Low muscle tone
Small stature and short neck
Flat nasal bridge
Single, deep creases across the center of the palm
Protruding tongue
Large space between large and second toe
A single flexion furrow of the fifth finger.
Individuals with Down syndrome usually have cognitive development profiles indicative of mild to