Chromosome 9- tetrasomy 9p
Overview
Chromosome 9, Tetrasomy 9p is a very rare chromosomal disorder in which the short arm of the ninth chromosome (9p) appears four times (tetrasomy) rather than twice in all or some cells of the body. Individuals with a normal chromosomal make-up (karyotype) have two 9th chromosomes, both of which have a short arm ("9p") and a long arm ("9q"). However, in individuals with Chromosome 9, Tetrasomy 9p, four short arms (9ps) are present in cells rather than the normal two.
Symptoms
The symptoms of Chromosome 9, Tetrasomy 9p may vary greatly in range and severity from case to case. Associated abnormalities may include mild growth retardation, moderate to severe delay in the attainment of skills requiring the coordination of muscular and mental activities (psychomotor retardation), and/or moderate to severe mental retardation. In addition, the disorder may be characterized by various physical abnormalities, such as malformations of the skull and facial (craniofacial) region, abnormalities of the hands and fingers, skeletal malformations, and/or heart (cardiac) defects
Causes
Chromosome 9, Tetrasomy 9p appears to result from spontaneous (de novo) errors very early in embryonic development that occur for unknown reasons (sporadically).