Mosaicism and clinical genetics.

With the introduction of increasingly sensitive technologies for mutation detection such as chromosomal microarrays and next-generation sequencing, the importance of mosaicism for human disease is being more fully appreciated. Mosaicism can occur for any type of mutation, either at the chromosomal or DNA sequence level, and while in many cases mosaicism can modify the clinical effects of a syndrome, there are many alterations that can only occur in mosaic form as the mutation is lethal when present in every cell. Mosaicism can have a wide range of effects, from early pregnancy loss, to organ specific pathology, to modification of clinical syndromes. Recent evidence reveals that generation of mosaic alterations is associated with aging, and our ability to detect mosaic alterations sheds light on normal and pathologic changes across the lifespan.