Chromosome 9 trisomy syndrome. Trisomy 9.
Incidence
Very rare syndrome. Sporadic.
Clinical Characteristics
Chromosome 9, Trisomy Mosaic, also known as Trisomy 9 Mosaicism syndrome, is a rare chromosomal disorder in which the entire 9th chromosome appears three times (trisomy) rather than twice in some cells of the body. The term "mosaic" indicates that some cells contain the extra chromosome 9, while others have the normal chromosomal pair. Associated symptoms and findings may vary greatly in range and severity, depending on the percentage of cells with the extra chromosome. However, common features include growth deficiency before birth (intrauterine growth retardation); mental retardation; structural malformations of the heart that are present at birth (congenital heart defects); and/or distinctive abnormalities of the skull and facial (craniofacial) region, such as a sloping forehead, a bulbous nose, short eyelid folds (palpebral fissures), deeply set eyes, and/or low-set, malformed ears. The syndrome may also be characterized by musculoskeletal, genital, kidney (renal), and/or additional physical abnormalities. Chromosome 9, Trisomy Mosaic may be caused by errors during the division of a parent's reproductive cells (meiosis) or during the division of body tissue cells (somatic cells) early in the development of the embryo (mitosis). In summary, it is related to the presence of an additional (third) chromosome in an otherwise diploid chromosome 9 with psychomotor retardation and multiple abnormalities of the craniofacial structures, heart, skeletal system, extremities, and other organs. Includes mosaic trisomy 9 syndrome. Trisomy 9 and trisomy 9 mosaicism have similar phenotype.
Precipitants
None
Provocation Tests
None
Diagnostic Procedures
Karyotype. Trisomy 9 and trisomy 9 mosaicism.