Incontinentia pigmenti: transmission from father to daughter.

Incontinentia pigmenti (IP) is a well-described genodermatosis that occurs almost exclusively in females. IP is characterized by a distinctive skin eruption and a variable presence of multisystem abnormalities. Pedigree analysis is most consistent with an X-linked dominant trait that is lethal in males. However, 27 reports of IP in males have been published, excluding four patients who had Klinefelter's syndrome. It has usually been assumed that these rare affected males survive because of genetic mosaicism. Mosaic inheritance of IP is also strongly supported by the characteristic distribution of skin findings along Blaschko's lines. Only one case of father-to-daughter transmission has been previously reported. We report a second case of father-to-daughter transmission of IP. Chromosomal analysis of blood and fibroblasts from the father failed to provide evidence of genetic mosaicism.