18p- Mosaicism

Summary The case of a 5-month-old male infant with 18p- mosaic, who has intractable seizures and severe ophthalmological abnormalities in addition to many clinical manifestations usually described in the 18p- syndrome, is reported. The proportions of abnormal cells are 7–8% in blood and 55% in skin. About 35% of the short arm of chromosome 18 is deleted. To our knowledge the present report is the fifth one of 18p- mosaic. The main interest of this case resides in the fact that it shows a serious clinical picture despite the low proportion of abnormal cells in blood and the small degree of deletion of the short arm of chromosome 18.