Characterization of a derivative chromosome 17 by fish-technique.

We report a case with derivative chromosome 17 which could not be characterized by routine G-banding, since the additional material on 17q overlapped with chromosome bands 2q35 -->qter, 3p25-->pter, 4p15-->pter, 5q33-->qter, 7p15-->pter, 12p11.2-->pter, 14q24-->qter and 16q22-->qter. Therefore, whole chromosome paint and region specific probes were used to identify the abnormality by FISH-technique which revealed a 46,XY, der (17) t (4;17) (p15.2;q25) karyotype. The proband was partially trisomic for 4p15.2-->pter and monosomic for the distal 17q25-->qter regions. The major clinical features included: anti-mongoloid slanted palpebrae, coloboma of right iris, depressed nasal bridge, high arched palate, protruding tongue, micrognathia and small penis. The MRI of the brain revealed midly hypoplastic cerebellar vermis, and a normal septum pellucidum. The infant responded to therapy for hypoglycemia and was discharged under stable condition. Prior to cytogenetic evaluation the infant was not recognized as either "trisomy 4p syndrome" or "monosomy 17q syndrome".