This information is provided by the National Institutes of Health (NIH) Genetic and Rare Diseases Information Center (GARD).
Ring chromosome 22 is a rare condition caused by having an abnormal chromosome 22 that forms a ring. In this chromosome abnormality, a segment on the short (p) arm and a segment on the long (q) arm of 22 are missing. The amount of material lost varies from person to person. The remaining ends of chromosome 22 have joined together to make a ring shape. Chromosome 22 is an acrocentric chromosome, meaning that the centromere is near one end, creating a very small short (p) arm that does not contain genes that are relevant to development. Thus, only the lost genes on the long (q) arm matter. Knowing the breakpoint in the long arm is likely more helpful. Most cases are sporadic (happen by chance) and occur in people with no history of the condition in their family.
For more information, visit GARD.