Brief Introduction & Summary
Chromosome 22 Ring is a rare disorder characterized by abnormalities of the 22nd chromosome. Simply put, chromosomes are the structures that hold our genes. Genes are the individual instructions that tell our bodies how to develop and keep our bodies running healthy.
In every cell of our body there are 50,000 to 100,000 genes that are located on 46 chromosomes. These 46 chromosomes occur as 23 pairs. We get one of each pair from our mother in the egg, and one of each pair from our father in the sperm. The first 22 pairs are labeled longest to shortest. Each chromosome has a p and q arm; p (petit) is the short arm and q (next letter in the alphabet) is the long arm. The last pair are called the sex chromosomes labeled X or Y. Females have two X chromosomes (XX), and males have an X and a Y chromosome (XY). Therefore everyone should have 46 chromosomes in every cell of their body. If a chromosome or piece of a chromosome is missing or duplicated, there are missing or extra genes respectively. When a person has missing or extra information (genes) problems can develop for that individual's health and development. It is important to note that most chromosome abnormalities occur as an accident in the egg or sperm. Chromosome abnormalities can be inherited from a parent, like a translocation, or be 'de novo' (new in that individual). Since Alec's case is 'de novo' his two sisters and one brother do not have any abnormalities and are typically developing children.
A ring chromosome can happen in two ways. One is demonstrated in this picture; the end of the p and q arm breaks off and then stick to each other. The blue parts of each are lost thus resulting in loss of information. Second, the ends of the p and q arm stick together (fusion), usually without loss of material. However the ring can cause problems when the cell divides and can cause problems for the individual. It is also possible to have a ring and be apparently healthy with no delays in development. As with all chromosome abnormalities it depends on what is actually found, the size of the ring, how much material was lost, which chromosomes are involved etc.
Associated symptoms & findings of Chromosome 22 Ring may be extremely variable from case to case. However, the disorder is typically associated w/ moderate to severe mental retardation. Some affected may also have relatively mild, nonspecific physical (i.e, dysplastic) features, whereas others may have more distinctive, potentially severe physical abnormalities. According to reports in the medical literature, common findings include diminished muscle tone (hypotonia) & motor incoordination; unsteady manner of walking (gait); pronounced verbal delays; &/or certain malformations of the skull & facial (craniofacial) region. Such craniofacial abnormalities may include an unusually small head (microcephaly); vertical skin folds that may cover the eyes' inner corners (epicanthal folds); unusually large ears; and/or other malformations. Chromosome 22 Ring is usually caused by spontaneous or "de novo" errors very early in development of the embryo that appear to occur randomly for unknown reasons.