A 2 year old girl presented with developmental delay and subtle dysmorphic features suggestive of Wolf-Hirschhorn syndrome (WHS). High resolution chromosome analysis was normal in the child and both parents. Molecular analysis indicated that the child had not inherited a maternal allele of probes from 4p16, confirming the clinical diagnosis. Prenatal diagnosis in the next pregnancy showed that again the fetus had no maternal allele for probes mapping to 4p16. Fluorescent in situ hybridisation in the mother showed a submicroscopic translocation, t(4;10). A normal karyotype in a child with clinical features of WHS is an indication for further investigation.