What Is Trisomy 3 Mosaicism?

Trisomy 3 is an extremely rare genetic disorder in which the third chromosome appears three times rather than twice in the cells of the body, explains the National Organization for Rare Disorders. Symptoms vary greatly depending on the length and location of the duplicated portion of third chromosome. In general, children with this disorder have developmental delays, mental retardation, and abnormalities of the face and head.

Characteristic facial features of children with trisomy 3 include a short, wide head, widely spaced eyes, a receding lower jaw, an abnormally short neck and a low hairline. Other common features of trisomy 3 are abnormally low muscle tone, underdeveloped bones in the hands, genital defects, and heart or kidney defects, according to the National Organization for Rare Disorders. Many infants with this disorder have eye abnormalities such as glaucoma, cataracts, corneal opacities or involuntary eye movements.

Results of prenatal testing may indicate the presence of this condition, but diagnosis typically happens at birth or during early infancy, states the National Organization for Rare Disorders. Treatment of trisomy 3 varies based on the individual patient's needs, symptoms and physical abnormalities. Patients may require care from a variety of medical disciplines along with special education services, physical therapy and other services.