Characterization of a de novo partial trisomy 22q13-qter in a patient by microFISH.

Chromosomal microdissection and subsequent application of the generated probe for FISH (microFISH) allowed the characterization of a small extra band found by routine cytogenetic analysis on the short arm of chromosome 19 in a mentally retarded boy with various dysmorphic features. There is no cytogenetically visible loss of chromosome 19 material as verified by hybridization results using a subtelomeric probe for this region and therefore all anomalies found in the patient are most likely due to the partial trisomy of 22q13-qter. The approach used in this study should be generally applicable in comparable cases and allows a fast and straightforward identification of the origin of extra chromosomal material, which otherwise is very laborious or difficult to characterize. Clinical features of this 9-year-old patient such as mental and motor retardation, microcephaly, microphthalmia and hypogenitalism are compared with other cases showing this rare chromosomal aberration.