Genetic mosaicism in dermatology: Clinical utility of genetic testing of skin lesions.

Mosaicism is defined as the existence of two or more distinct clonal cell populations within one individual, which is the product of a single fertilised egg.[1] Mosaicism is an acquired mutation during embryonic development and can be classified according to reproductive risk: I somatic i mosaicism is limited to non-reproductive cells; I gonadal i mosaicism is found only in reproductive cells and can be expressed constitutionally in future generations, and I gonosomal i mosaicism is in both.[[1]] Mosaic presentations of genetic disorders are often observable in a segmental form in the skin, due to post-zygotic I de novo i mutations.[1] Thus, cutaneous mosaic disorders offer a unique opportunity to investigate genetic mosaicism. Mosaicism of single gene disorders explains segmental skin lesions in a range of heritable skin disorders. A mutation was identified in DNA derived from skin biopsies, which was not present in peripheral blood DNA in five of these six cases. [Extracted from the article]