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Penta X syndrome is a rare disorder since less than 10 cases have been reported. This communication describes an additional case of pentasomy X in a three-week old white female infant born at full term to a 22 year old mother. The birth weight was 3000 grams. Abnormal findings in the patient were hypertelorism, micrognathia, rather small and drawn back ears, simian creases, bilateral clinodactyly and congenital heart disease (tetralogy of fallot). The phenotype of this infant was distinct from that seen in Down's Syndrome. There is no family history of birth defects or other congenital anomalies. One to four Barr bodies were observed in her buccal smear analysis. Cytogenetic analysis of the peripheral blood and skin by Giemsa banding revealed a 49,XXXXX karyotype with no mosaicism or structural abnormality. Both parents and a 2 year old male sibling were also analyzed by C- and G-banding. The sibling had a normal karyotype. However, the mother's karyotype showed 8 percent 47,XXX, and the father's karyotype 6 percent 47,XXY along with a normal genetic complement. The majority of polysomies are due to double non-disjunction in oogenesis, but in this case either one or both parents may have contributed toward the anomaly.

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Muneer, R., Stone, J., Stupca, P. et al. 745 A PENTA X FEMALE (49, XXXXX): A RESULT OF PARENTAL MOSAICISM?. Pediatr Res 15, 566 (1981).

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