Experiences of CMN
Living with Congenital Melanocytic Naevi (CMN), as a rare disease, is different for everyone and therefore how we can best provide support depends on these variable experiences. CMN has many different types leading to differing experiences for those affected.
For some, CMN is found solely on the skin as a dark brown birthmark covering up to 80% of the body and in varying forms, such as flat, raised, lumpy, hairy, itchy, and fragile. Raised and lumpy CMN can be limiting for our members and can affect mobility. Skin can be very itchy and often affects sleep as a result.
There is also a small increase in the risk of developing melanoma when CMN is present on the skin. While the overall risk is low, when melanoma does develop in CMN it is highly aggressive.
CMN can also affect body systems beyond the skin, causing medical complexities which can involve neurological problems. These can be challenging to life and in the worst cases can be fatal.
Dependent upon the type of CMN, surgery may be considered. As a charity, we are here to support our members, whatever their experience. This article hopes to further explain how CMN can vary and lead to a broad range of experiences.
Genetic cause of CMN
The outworking of Mosaic Disorders which affect the skin are currently the best known as it is possible to see the effects on the skin as a birthmark. As a result, although they often affect many body systems as well as the skin, Mosaic Disorders are looked after by dermatologists. This Rare Disease Collaborative Network (RDCN) focuses on the severe end of the spectrum of these diseases.
An MRI scan is recommended for all children born with multiple CMN to determine the presence of any pigment in the brain or nervous system. An earlier MRI allows for a clearer scan. MRI results can be used as a framework for the child’s development and can determine whether CMN is also present internally.
Currently, there is no definitive treatment for CMN. As a charity we partner with Professor Kinsler and her research team at Great Ormond Street Institute of Child Health and The Francis Crick Institute to fund the CMN research taking place. In recent years, the causes of CMN have started to be understood by the CMN research team studying the genes in CMN cells through skin biopsies, donated by people with CMN.
These studies have found that in 67% of the people studied, there were changes (known as mutations) in a gene called NRAS; this was found to be the most common cause of CMN of any size and any number. Changes to the
BRAF gene has been found as a cause for 7% of CMN. In some patients, there are no spelling mistakes, but instead two genes get stuck (fused) together, which should not happen. These fusions are responsible for the CMN being very itchy and forming lumps or ridges. This phenomenon stops the gene from performing its normal function and causes the skin problems associated with CMN, this is known as a BRAF Fusion.
Raised and itchy CMN
Skin cells containing BRAF gene fusions have been found to grow much faster than cells containing NRAS/BRAF spelling mistakes or no mistakes at all.
This could explain why some members develop lumps and ridges, as the cells with the fusions divide excessively. The CMN can also be very itchy.
Risk of melanoma
Melanoma is a cancer of the melanocytes; the skin cells which produce pigment and make up CMN. Melanoma in children with CMN can occur anywhere, not just the skin and is unfortunately usually aggressive and difficult to treat.
The overall risk of melanoma in people with CMN is low but the risk is higher in people with brain or spine disease found on MRI after birth and there is a peak of risk during childhood.
It can present as a lump in the CMN or another area of the skin, in the lymph nodes (which are throughout the body) or in the brain and spine.
Nodular growths can occur within the CMN which can lead to uncertainty and anxiety for those affected as to whether they are malignant or benign. It is acknowledged that the histology of CMN (studying the cells under a microscope) is often difficult and therefore it is recommended that a review be carried out by at least two experts in the field. A genetic analysis of an individual’s CMN can help to differentiate melanoma from benign nodules in the skin, and from stable congenital disease in the Central Nervous System.
CMN syndrome
A syndrome is a collection of findings in one individual that can potentially be explained by the same genetic change. The term CMN syndrome alerts healthcare professionals to aspects other than the skin.
Overall, neurological problems (in the brain or spinal cord) are the most common medical complexity seen in children with CMN. Most seen is pigment-containing cells (like a CMN) in the substance of the brain. This is called benign intraparenchymal
melanosis. (moles in the brain)
Other rare neurological problems include benign brain or spinal tumours, too much fluid in the brain (hydrocephalus), or abnormal brain structure. All of these are more common with larger and more numerous CMN.
Neurological problems associated with CMN used to be called Neurocutaneous melanosis. This term is no longer used by Professor Kinsler’s CMN clinic in the UK for two important reasons. The first reason is that some of the problems are not actually “melanosis,” in other words they are not a problem of pigment cells. The second reason is that in the medical literature neurocutaneous melanosis is often actually melanoma of the brain or spinal cord, which has caused confusion whilst advising families on diagnosis. We now prefer to call the neurological problems by their actual names such as benign intraparenchymal melanosis (e.g. moles in the brain) or melanoma of the brain or spine This allows medical professionals to give better information to parents and patients and to categorise the cases due to best care and complexity.
Our current recommendations are that any child born with two or more CMN should have a routine MRI scan of the brain and spine, preferably by the age of 6 months. The reason for doing the scan is to pick up the rare cases of tumours and extra fluid on the brain that require an operation, and to allow medical professionals to monitor development more carefully in children with abnormal MRI findings, sometimes with more MRIs.
The overall chance of finding an abnormality on an MRI scan in children with multiple CMN (two or more at birth) is around 20%, but only around half of these children will have any neurological involvement. If they do, these can be fits (convulsions), developmental delay, or problems with their limbs. It is possible to experience issues with development even when the scan is typically normal, but these tend to be milder. Most children will only require one scan but anyone with multiple CMN who develops new issues with development, fits, limbs or persistent headaches over a long period of time should have a repeat MRI.
Research into CMN syndrome has also found that there are characteristic facial features of children with CMN, some increased weight gain in children and subtle hormonal problems.
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Support available
Our vision is to live in a world where no one suffers with CMN through providing tailored support for every type and experience of CMN, educating the healthcare profession about CMN, changing negative perceptions of CMN as a visible difference, and developing effective treatments for all types of CMN.
If you or your child has been diagnosed with any of the above medical complexities due to CMN, there is dedicated support available. Please contact the charity’s support helpline 0300 373 3422 or email support@caringmattersnow.co.uk
