Mild phenotype and normal gonadal function in females with 4p trisomy due to unbalanced t(X;4)(p22.1;p14).

In this report we describe the mild phenotypic manifestations and normal gonadal function in a 50-year-old mother and her 17-year-old daughter with 4p trisomy resulting from an unbalanced t(X;4)(p22.1;p14) mat. Late replication of the der(X) was demonstrated by BrdU incorporation with spreading of the late replication to the 4p portion as an explanation of the reduced effect of the trisomy 4p/monosomy Xp on the physical and secondary sexual development in both patients.