Noninactivation of a portion of Xq28 in a balanced X‐autosome translocation

We present a balanced translocation (X;9) (q28;q21) in which the normal X chromosome is preferentially active. The derivative X chromosome is inactive in 93% of fiibroblasts, but the X portion translocated onto chromosome 9 is not inactivated, as apparent from DNA methylation and chromosome replication patterns. Consequently, the patient is functionally disomic for the part of Xq28 distal to the locus LICAM