Manifestations of mosaicism
Mosaicism, the presence of two or more genetically different cell lines, is a common phenomenon associated with a protean range of physical and developmental effects. This presentation will be an overview of the many manifestations of mosaicism concentrating on those presenting with dysmorphic features.
In individuals with mosaicism not all cell lines have chromosomal or single gene differences; other mechanisms resulting in functional differences may apply such as aberrant X-inactivation, and mitotic recombination in imprinted regions of the genome. Of particular interest are disorders inherited in an X-linked dominant fashion with male lethality where survival of females is due to mosaicism
A number of common clinical features are found in many patients with mosaicism regardless of the underlying genetic abnormality. These include body and limb asymmetry, skin pigmentary markings and other lesions in the distribution of Blaschko’s lines. Also frequently observed are joint contractures, truncal obesity and various eye and central nervous system signs and symptoms.