The genetic cause of a rare condition, which causes large moles to grow on the skin and brain before birth and which increases the risk of melanoma, has finally been identified in a study led by Dr Veronica Kinsler at Great Ormond Street Hospital (GOSH) and the UCL Institute of Child Health (ICH).
The findings will help clinicians to develop tests for the condition and may help develop treatments for people living with the condition, known as multiple congenital melanocytic naevi or CMN.
CMN can be difficult to live with for children and their families, as the CMN are large dark brown marks on the skin. More seriously, they can also lead to neurological problems such as fits and developmental delay, and to malignant melanoma (skin cancer) which is usually fatal when it occurs.
Poppy’s life with CMN
Six-year-old Poppy, is a Great Ormond Street Hospital patient with CMN, as her mum Kirsty explains: “Poppy was diagnosed with CMN when she was 14 weeks old. When we found out about the CMN, we were told there were two issues: an increased risk of skin cancer, and a possible risk of developmental delay. I wasn’t concerned as much about the second as I was about the first, and as it turned out, a brain scan showed no signs of complications.”
“When she was younger we hardly went out, because I was so worried about her being exposed to the sun, particularly given that her main birthmark is on her head. But now I’m much more confident. Poppy has just turned six, so she needs to get out and get her vitamin D from the sun.
“We’ve discovered that she doesn’t burn easily, but we still put lots of sun cream on her, as well as a sun hat and a protective suit with long sleeves, so that only her feet and hands are exposed.”
No treatment is currently available for patients who have many large CMN, but doctors monitor patients carefully for signs of skin cancer, and use MRI to scan the brain for lesions. Small moles can be removed by surgery, but larger areas cannot normally be removed this way. Laser treatment is not an option, as the CMN are too deep to be removed completely.
Kirsty says that Poppy is closely monitored: “We get support from our local hospital and GP as well as GOSH, so the fact that she is checked every six months means that any signs of changes in her skin should be picked up.”
Research breakthrough
The breakthrough is the discovery that this condition is caused by a mutation in a gene called NRAS, which occurs while the baby is growing in the womb. This gene mutation was found in 80% of the patients who took part in the study. The other 20% are still being investigated to determine the cause of the condition in their cases.
The gene pinpointed in the ICH-led study is known to be involved in the development of melanomas in the normal population, but has never been found before to occur during the development of a baby.
It explains why patients with CMN have an increased risk of melanoma, and the researchers found that the patients need to develop a second mutation to change the moles into cancer.
Dr Veronica Kinsler, Paediatric Dermatologist at GOSH and the ICH and lead author of the study says: “This is a big breakthrough for people who have CMN. The discovery of the genetic mechanism means we can now develop tests to differentiate between people carrying this gene and those who don’t, and finally we can start to look for new ways to treat this serious condition.”
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