Wolf-Hirschhorn syndrome owing to 1:3 segregation of a maternal 4;21 translocation

We describe a child with Wolf-Hirschhorn syndrome with the karyotype 45,XY,inv(9)(p11q13)pat,-4,-21,+der(4),t(4;21)(p15.3;q11.2)mat. This is the second case known to us of Wolf-Hirschhorn syndrome caused by 1:3 segregation of a parental rearrangement. This mode of segregation can be predicted in both cases by a pachytene-diagram model. It is uncertain whether or not the proximal 21q monosomy in this case has affected the phenotype.