Apparently normal chromosomes without a molecular 4p16.3 deletion were found in a patient with a Wolf-Hirschhorn syndrome (WHS) phenotype. During a 10-year-period of observation he consistently presented with typical facial appearance, moderate to severe mental retardation, normal physical development with normal head circumference. Genetic results and the relatively mild clinical manifestations suggest that a diagnosis of Pitt-Rogers-Danks syndrome (PRDS) may be more likely in this patient. If WHS and PRDS will ultimately prove to be caused by haploinsufficiency of the same gene in 4p16, non-deleted patients such as the present one will be good candidates for the search of point mutations in such putative gene.