There has been a very exciting new finding in our study of the genetics of congenital melanocytic naevi (CMN).  We have discovered that the genetic change (called a mutation) that causes CMN and neurocutaneous melanosis is in a gene called NRAS.  We found this gene mutation in 80% of the cases we looked for it in the skin, and also in the brain when there were problems there.  In 20% of cases we still do not know what the gene is.

This gene mutation is not present in the blood samples from people with CMN, only in skin or brain.  We have only so far been able to look for this in 15 people, from whom we had consent to check their samples, but we are now checking it in stored samples in the hospital where people have also given their consent.

The NRAS gene is already known to be involved in melanoma, but does not cause melanoma on its own. NRAS is an important gene in the body which acts as a switch to turn on cell growth.  With the mutation in the gene the effect is to keep that switch always on.  When this happens during foetal development in a particular cell it produces CMN.

I am going to be talking about this new finding at all the Caring Matters Now family days from now on, and I will also be happy to discuss it at clinic appointments.  Caring Matters Now local contacts can also help to explain the finding. This finding is going to help us to move the project to the next phase, which is to start looking for treatments for CMN.

I would like to thank all the families who have been involved in the research studies, and given blood samples and skin samples. It is not an easy thing to ask your child to give a blood sample, or a skin sample, and not easy for the child to do.  It is not possible to over-state their role in this research, as we would simply not have been able to find this gene without the samples.  I would like to mention two families who gave samples in very difficult personal circumstances, to whom we are all particularly indebted – these are the Bostock and Wigmore families. Without their samples the research would not have been able to draw the conclusions that it did, with the resultant benefit for all people with CMN.


With best wishes

Dr. Veronica Kinsler

Here is the link to the summary of the publication released:

Multiple Congenital Melanocytic Naevi and Neurocutaneous Melanosis are Caused by Post-Zygotic Mutations in Codon 61 of NRAS

Great Ormond Street uncover findings on their blog: