Owing to its accessibility, the skin offers unique opportunities to observe and study the phenomenon of mosaicism. This seems to be more frequent than we used to believe. However, one must be aware of it to “see ” it. The term mosaicism refers to the presence in an individual of 2 (or more) genetically distinct cell populations derived from the same zygote.1 In the 1980s, excellent clinicians provided clinical observations on mosaic patterns in the skin. It was Rudolf Happle, MD, who postulated new genetic concepts on mosaicism in skin, long before molecular genetic evidence was available. He also delineated the X-dominant chondrodysplasia punctata, known also as Conradi-H ünermann-Happle syndrome (CDPX2 [OMIM 302960])2 and predicted the significance of Blaschko lines.3 In the years 1977 to 1981, the main characteristics of CDPX2 were described: the X-linked dominant inheritance pattern and the multiple organ involvement associating linear ichthyosis following the lines of Blaschko, chondrodysplasia punctata, cataracts, and short stature.2,4,5 The interpretation of the asymmetry of skeletal abnormalities, cataracts, and linear skin lesions, as consequences of functional mosaicism resulting from X-inactivation,6 was also a remarkable achievement.
Has C. Mosaicism in the SkinThe Importance of Mild or Minimal Skin Lesions. Arch Dermatol. 2011;147(9):1094-1096. doi:10.1001/archdermatol.2011.233