The second type is called Translocation Trisomy 21. This type occurs when the extra 21 chromosome breaks off during cell division and attaches to another chromosome. This is the only type of Down syndrome that can result from a condition in the parent's genes. Two to three percent of children with Down syndrome have this type. The third and least common form of Down syndrome is known as Mosaicism. This type occurs in only one to two percent of all people with Down syndrome. In Mosaicism, a faulty cell division occurs in one of the early cell divisions after fertilization. As in Nondisjunction Trisomy 21, something causes the cells to divide unevenly. But when this occurs in the second or third cell division, only some of the cells contain the extra chromosome. The percentage of cells affected differs from child to child. .
Individuals with Down syndrome may be identified by numerous physical attributes which may or may not present themselves in any one individual. Some characteristics are the almond shaped eyes, Brushfield spots on the irises, a singular palmer crease on one or both hands, small features, a tongue that seems too large for the mouth, a short neck, the head may be flattened in the back, small ears that may be folded at the top, and exceptional social intelligence. .
Individuals with Down syndrome are more apt then the general public to have conditions that require medical supervision. Many have congenital heart defects and should have an echo cardiogram during the first two months of life. Other conditions may be hearing loss, vision impairments, upper respiratory infections, diabetes, and leukemia. Babies and children with Down syndrome acquire early and extensive health evaluations. .
Some other factors that are important to note about children with Down syndrome are that they are more similar to the average child in the community than they are different.
