IDENTIFICATION OF AN UNBALANCED CRYPTIC TRANSLOCATION T(9-17)(Q34.3-P13.3) IN A CHILD WITH DYSMORPHIC FEATURES

We report a case of an unbalanced cryptic telomeric translocation 46,X Y,der(17),t(9;17)(q34.3;p13.3) in a boy with dysmorphic features and d evelopmental delay. The proband had intrauterine growth retardation, p ostnatal short stature, and mild microcephaly. Magnetic resonance imag ing showed incomplete myelination, but no evidence of lissencephaly. C ytogenetic analysis of the proband's peripheral blood showed an abnorm al 17p. Fluorescence in situ hybridisation (FISH) with a Miller-Dieker cosmid probe did not detect a deletion for that area. Further analysi s with a 17p telomere specific probe identified an unbalanced telomeri c translocation. The same probe was used to determine the presence of an apparent balanced translocation t(9;17)(q34.3;p13.3) in the mother of the proband. The balanced translocation was confirmed with two cosm ids that map distally on 9q34.3. Two phenotypically normal half sibs, a maternal aunt, a maternal uncle, and the maternal grandmother were f ound to be balanced translocation carriers as well. A subtle transloca tion is one mechanism that can produce an abnormal phenotype in a pati ent who had normal karyotype at lower band resolution levels.