RT Journal Article SR Electronic T1 Epidermal mosaicism and Blaschko's lines. JF Journal of Medical Genetics JO J Med Genet FD BMJ Publishing Group Ltd SP 752 OP 755 DO 10.1136/jmg.30.9.752 VO 30 IS 9 A1 C Moss A1 S Larkins A1 M Stacey A1 A Blight A1 P A Farndon A1 E V Davison YR 1993 UL http://jmg.bmj.com/content/30/9/752.abstract AB To test the hypothesis that epidermal rather than dermal mosaicism determines Blaschko's lines in hypomelanosis of Ito (HI), we studied the distribution of chromosomal mosaicism in four patients. In two, mosaicism had not been detected in lymphocytes or dermal fibroblasts, but was clearly shown in epidermal keratinocytes; furthermore, the abnormal cell line was confirmed to the hypopigmented epidermis and the normal epidermis contained only normal cells. Negative findings in the other two patients might be because of mosaicism which was undetected either because it was submicroscopic or because it was present in melanocytes, which have not yet been studied. These preliminary results support the ideas that (1) Blaschko's lines represent single clones of epidermal cells; (2) in patients with HI and severe neurological involvement mosaicism, if detectable, is best shown in keratinocytes; and (3) the cytogenetic defect in epidermal cells may be directly responsible for the failure of pigmentation in HI.