TRISOMY 10QTER CONFIRMED BY IN-SITU HYBRIDIZATION

We report a boy with multiple congenital anomalies compatible with tri somy for the distal region of the long arm of chromosome 10 and a male karyotype with one 18p+. In situ hybridisation with a cDNA for ornith ine aminotransferase (OAT), whose locus maps to 10q26, confirmed the c linical suspicion of distal trisomy 10q. Subterminal localisation of t he labelling signals on chromosome 10 and on the der(18) indicated the localisation of the OAT locus in the proximal part of 10q26. Two clus ters of labelling signals were also found on the pericentromeric and p roximal portion of the X chromosome short arm, thus confirming the pre sence in this region of two non-adjacent OAT pseudogenes. The phenotyp ic similarities of this patient to previously reported cases provide f urther support for the delineation of trisomy 10qter as a specific, cl inically recognisable syndrome.