We present here a 6-year-old girl with the clinical signs of Wolf-Hirschhorn syndrome (WHS). Only after FISH studies the suspected 4p16.3 deletion could be confirmed. FISH studies in the mother showed that she was carrier of a balanced/unbalanced mosaicism with a 4p/16p translocation in 60% of the cells, and 4p16.3 deletion in 40% of the cells.