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Vol. 20, No. 3, 2005
Issue release date: May–June 2005
Fetal Diagn Ther 2005;20:219–222

Tetrasomy 9p Mosaicism Associated with a Normal Phenotype

McAuliffe F. · Winsor E.J.T. · Chitayat D.
aDepartment of Obstetrics and Gynecology, Mount Sinai Hospital, University of Toronto, Toronto, Canada; bDepartment of Obstetrics and Gynaecology, National Maternity Hospital, University College Dublin, Dublin, Ireland; cPrenatal Diagnosis and Medical Genetics Program and dDepartment of Pathology and Laboratory Medicine, Mount Sinai Hospital, University of Toronto, Toronto, Canada

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Isochromosome (tetrasomy) 9p is a rare chromosomal aberration characterized by phenotypic abnormalities ranging from mild developmental delay to multiple anomalies including intrauterine growth retardation, cerebral ventriculomegaly, dysmorphic facial features, cleft lip or palate, abnormal genitalia and renal anomalies. We present a patient with isochromosome (tetrasomy) 9p mosaicism who is a healthy normal adult male with oligospermia who has fathered two normal children. This chromosomal abnormality may be tissue specific, with a higher detection rate in cultured lymphocytes compared with fibroblasts. Therefore, there is an increased chance of missing the abnormality prenatally by amniocentesis or chorionic villus sampling. We are aware of only one other patient in the literature with a normal phenotype associated with mosaicism for this chromosomal abnormality.

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