Distal monosomy 18p/distal trisomy 20p - A recognizable facial phenotype?

We describe an 8.5-year-old boy with facial dysmorphism consisting of a round and flat face, telecanthus, periorbital fullness, short nose, downturned corners of the mouth, and micrognathia. In addition, profound mental retardation, tetralogy of Fallot, and renal dysplasia were present. Tentative clinical diagnoses during the 6-year follow-up included Down, Hennekam, and Noonan syndromes. Refinement of cytogenetic techniques, especially increase of banding resolution in conventional cytogenetic analysis, gave the clue to the correct diagnosis, which was proven by fluorescence in situ hybridization (FISH) with whole chromosome paints and single copy probes. We could show that he had an unbalanced translocation inherited from his father resulting in partial monosomy 18p and partial trisomy 20p. The combination of deletion 18p/duplication 20p was previously reported in three patients and seems to have a clinically recognizable face.