HYPOMELANOSIS OF ITO AND X-AUTOSOME TRANSLOCATIONS - A UNIFYING HYPOTHESIS

Hypomelanosis of Ito is a sporadic multisystem disorder known to be as sociated in many cases with chromosomal mosaicism. While no particular pattern is generally evident for the specific chromosomes involved in such patients, a subgroup of female patients exists in whom the commo n factor is the presence of a balanced, constitutional X;autosome tran slocation, with a cytogenetic breakpoint in the pericentromeric region of the X. It is argued here that the phenotype in these cases results not from the interruption of X linked genes but from the presence of mosaic functional disomy of X sequences above the breakpoint.