The genes mutate either spontaneously or under the influence of mutagenic agents (irradiation, viruses, toxins).
The occurrence of genetic syndromes in the scope of one family is pointing more to the inherited than to de novo mutation.
Aim of this study was to present two syndromes in the same family tree, occurring subsequently one by one, which carry severe mental retardation and have a poor prognosis and frequently tragic outcome. A case report was given of a patient in
whom both pregnancies were completed by birth of the newborns presenting with severe syndromes: the first one with
Down's syndrome and the second one with Prader-Willi-Labhart syndrome. The results of investigation point to the necessity of genetic investigations before pregnancy and during pregnancy as early as possible, in order to avoid giving birth to
the children with syndromes which bear severe mental retardation and having poor prognosis.