De novo simultaneous reciprocal translocation and deletion.

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Abstract
A female infant with severe mental retardation, general hypotonicity, and a history of generalized edema, cyanosis, heart murmur, and nystagmus in the 1st days of life was found to have both a translocation and a deletion. Her karyotype was 46,XX,del(21)t(18;21)(18;21)(18p ter.fwdarw.-18q11::21q21.fwdarw.21q ter;21p ter.fwdarw.21q11::18q11.fwdarw.18q ter). The karyotype of both parents was normal. The proposita is the result of a 3 break point exchange and is monosomic for part of the dark band q11 q21 of chromosome 21. In cases with mental retardation and apparent balanced de novo reciprocal translocation, a small undetected deletion in one of the chromosomes involved in the translocation may explain the mental retardation.