RudolfHappleMosaicism in human skin: Understanding nevi, nevoid skin disorders, and cutaneous neoplasia2014Springer VerlagHeidelberg, Germany978-3-642-38764-7229 pages. $154.95

Abstract

Some books simply need to be written. This is one of them. For the past 4 decades, Rudi Happle has advanced the concept of mosaicism in skin disease through a series of creative papers. It must be gratifying to him to see how many of his postulates and theories have been proven during this time. Mosaicism in Human Skin brings his many creative ideas and new diseases all together in 1 place. In addition, he has accumulated a superb collection of clinical illustrations that greatly enhance the text.I can recall how in the mid-1970s, when I was a resident with Bob Goltz, both Happle and Robert Jackson wrote papers linking Blaschko lines and mosaicism. I had seen several patients with focal dermal hypoplasia (Goltz syndrome) and incontinentia pigmenti, but had never heard of Alfred Blaschko and his developmental lines. Instantly, I knew this was the answer to the peculiar skin and even radiographic findings in these 2 diseases and other X-linked dominant disorders.Happle explores Blaschko lines in great detail, explaining the original contribution, the different patterns, their manifestations in skin, bone, teeth, and even retina, and in animals as common as dogs and as exotic as dwarf zebus. He also clearly explains the differences between genomic mosaicism and epigenetic mosaicism—the most common example being X-chromosome inactivation in females.Although mosaicism is often associated with exotic terms like didymosis (twin spotting) and phacomatosis pigmentokeratotica, one should not conclude that it is not of everyday importance. For example, distinguishing between type 1 and 2 segmental manifestations of autosomal dominant disorders is crucial because the latter is much more likely to be transmitted to offspring. Moreover, many common polygenic disorders, such as psoriasis or atopic dermatitis, may likewise show a superimposed linear or otherwise mosaic involvement. Another key concept is the presence of autosomal dominant lethal mutations that can only be expressed as mosaics; examples include McCune–Albright and Sturge–Weber syndromes. At an even more practical level, as the subtitle suggests, mosaicism helps us understand nevi and cutaneous malignancies.I cannot imagine a better book on mosaicism ever being written. If you are at all curious, take a look at Rudi Happle's masterpiece, Mosaicism in Human Skin. Some books simply need to be written. This is one of them. For the past 4 decades, Rudi Happle has advanced the concept of mosaicism in skin disease through a series of creative papers. It must be gratifying to him to see how many of his postulates and theories have been proven during this time. Mosaicism in Human Skin brings his many creative ideas and new diseases all together in 1 place. In addition, he has accumulated a superb collection of clinical illustrations that greatly enhance the text. I can recall how in the mid-1970s, when I was a resident with Bob Goltz, both Happle and Robert Jackson wrote papers linking Blaschko lines and mosaicism. I had seen several patients with focal dermal hypoplasia (Goltz syndrome) and incontinentia pigmenti, but had never heard of Alfred Blaschko and his developmental lines. Instantly, I knew this was the answer to the peculiar skin and even radiographic findings in these 2 diseases and other X-linked dominant disorders. Happle explores Blaschko lines in great detail, explaining the original contribution, the different patterns, their manifestations in skin, bone, teeth, and even retina, and in animals as common as dogs and as exotic as dwarf zebus. He also clearly explains the differences between genomic mosaicism and epigenetic mosaicism—the most common example being X-chromosome inactivation in females. Although mosaicism is often associated with exotic terms like didymosis (twin spotting) and phacomatosis pigmentokeratotica, one should not conclude that it is not of everyday importance. For example, distinguishing between type 1 and 2 segmental manifestations of autosomal dominant disorders is crucial because the latter is much more likely to be transmitted to offspring. Moreover, many common polygenic disorders, such as psoriasis or atopic dermatitis, may likewise show a superimposed linear or otherwise mosaic involvement. Another key concept is the presence of autosomal dominant lethal mutations that can only be expressed as mosaics; examples include McCune–Albright and Sturge–Weber syndromes. At an even more practical level, as the subtitle suggests, mosaicism helps us understand nevi and cutaneous malignancies. I cannot imagine a better book on mosaicism ever being written. If you are at all curious, take a look at Rudi Happle's masterpiece, Mosaicism in Human Skin.