[Numerical and structural anomalies of chromosome no. 18 (author's transl)].

Two newborn babies with trisomy 18 and one with a deletion of the short arm of chromosome 18 (Syndrome 18p-) were admitted within 3 months to the Westfälische Landeskinderklinik Bochum. Under this aspect the clinical appearance of numerical and structural anomalies of chromosome 18 is described. Clinical symptomatiology which is rather typical for Trisomy 18 (Edwards syndrome) so that a diagnosis may be made in many instances even before the result of chromosomal analysis is available is compared with the facts given in the literature. The 83 cases of syndrome 18p- published so far are presented in a table. The absolute frequency compared with conceptional age of the mother gives a 2 peak distribution curve with one maximum between 25 and 29 years and one between 40 and 45 years. Similar patterns indicating two different ways of pathogenesis were described for trisomy 18 and 21. Furthermore patients suffering from syndrome 18p- show an increased incidence of IgA deficiency, which is 1:2 compared to 1:500 to 1:700 in an unselected population.