New research, using data from Children of the 90s at the University of Bristol, has identified that the gene causing red hair is more common in children with a rare form of birthmark, medically known as Congenital Melanocytic Naevi. 

The research was carried out at Great Ormond Street Hospital and the UCL Institute of Child Health and the changes in the gene causing red hair (MC1R) were found to be more common in children with CMN, and in their families, than those without the condition based on nearly 500 cases.

Dr Veronica Kinsler, who runs the paediatric pigmentary service at GOSH, said: "CMN is a very rare condition, and currently there are no good medical treatments for it.  In order to find treatments we need to understand what caused the birthmarks to occur in the first place, and therefore we are investigating the genetics of CMN.

"This study shows an association between the gene that causes red hair and CMN.  The gene seems to make CMN more likely to develop, particularly if the child has inherited a copy of the gene from each of their parents.  Also some variants of the gene are associated with the CMN being larger.

"If you have red hair in your family, these findings should not worry you, as changes in the red hair gene are common, but large CMN are very rare.  So the changes do not cause the CMN to happen, but just increase the risk."

CMN are rare brown or black birthmarks which cover up to 80 per cent of the skin surface area and can occur anywhere on the body. The incidence of larger or multiple lesions is approximately 1 in 20,000 new births per year.

An unexpected finding in the study was that the same changes in the red hair gene that  were associated with larger birthmarks also seem to have a more general effect on foetal growth - babies with those particular changes had a significantly higher birth weight than those without.  This was confirmed in both the CMN group and in the control group from Children of the 90s.

Dr Kinsler added:  "The effect on birthweight was a complete surprise.  We looked for it when we noticed that certain changes in the gene were associated with the CMN being larger, and wondered if they affected growth more generally.  However, it is important to stress that this is a relatively small study for looking at birthweight, and we are now checking this finding in a much larger group of people without CMN."

Doctors at Great Ormond Street Hospital estimate there are only around 3,000 individuals with severe CMN at the moment in the UK, with lots more who are mildly affected.

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Posted 11/05/2012 by