Mosaic disorders are a group of rare disorders caused by a genetic mutation (change, sometimes also called a genetic variant) in a single cell in the developing baby during pregnancy. This leads to the baby being born with a mixture of normal cells (not carrying the mutation) and disease cells (carrying the mutation). It is this mixture which is referred to as mosaicism. This is a random mutation and is not inherited from either parent.
The effects of the mutation depend on lots of different things. The most important ones are when it occurs and whereabouts it occurs in the body. In general, the earlier the mutation happens, the more serious the disease will be. As a result of the variability, each child with a mosaic disorder is unique in their disease and needs to be assessed uniquely. Mosaic disorders affecting the skin are currently the best known because it is possible to see the effects on the skin as birthmarks. As a result, although they often affect many body systems as well as the skin, mosaic disorders affecting the skin are looked after by Paediatric Dermatologists and Dermatologists. The Rare Disease Collaboration Network (RDCN) focuses on the severe end of the spectrum of these diseases, this clinic can be accessed by adults with CMN at Guys Hospital and for children with CMN through GOSH.
