Interchange trisomy 22 in a live born resulting from 3:1 segregation in a t(15;22) (p12;q13) carrier mother.

Non-mosaic Trisomy 22 is the second most common autosomal trisomy found in spontaneous abortions but relatively uncommon in live births. We report a case of non mosaic trisomy 22 surviving till late infancy. The unique phenotype was microcephaly, large eyes with anti mongoloid slants, mild hypertelorism, broad depressed nasal bridge, large prominent bulbous nasal tip anteverted nostrils, long philtrum, small mouth with down turned corners, microretrognathia cleft palate and preauricular tags. Systemic examination showed a ventricular septal defect. The probands karyotype was 47, XX, der(15)t (15;22) (p12;q13),+der(22)mat. This karyotype is as the result of 3:1 interchange segregation in the mother who is a carrier of a balanced translocation. The proband had inherited two derivative chromosomes and extra chromosome from the mother besides one 22 from the father. This is known as interchange trisomy. We report the first such case from India discussing the possible reason for the late survivor of this usually lethal anomaly.