Inherited translocation t(4;5) discovered on prenatal diagnosis.

We report an apparently balanced reciprocal t(4q;5q) translocation ascertained coincidentally on amniocentesis in a phenotypically normal male fetus and found to be inherited in his mother and maternal grandmother. No banding study was available at the time of the amniocentesis, and the chromosomal status of his parents was unknown. Because of the possibility that this finding might be a de novo, unbalanced translocation, the pregnancy was terminated. Subsequently, the translocation was found to be apparently balanced, but so unequal that both unbalanced translocation products are presumed to be lethal. Thus, it is predicted that only carriers and normal individuals will be conceived and viable in this family. We are unaware of previously observations on a similar (4q;5a) translocation.