In the diagram below, the two chromosomes of each parent are shown. The gene for Gorlin syndrome with the faulty gene is coloured in red, the “normal” genes in white. Each child with the syndrome inherits either the faulty or the normal gene from the parent with the syndrome. But why am I the only person affected in my family? In some families, only one person appears to be affected. It could be because either parent had the syndrome, but the effects were so mild it was never diagnosed. The fault in the gene probably happened for the first time at conception. This is called the result of a “new mutation” and this happens fairly frequently to the Gorlin syndrome gene. Children of someone who is the first person to be affected can inherit the faulty gene. The risks are shown above. Other members of the family (parents, brothers and sisters of the affected person) may not be at risk. In these circumstances there will no need for screening for the basal cell carcinomas or jaw cysts. A referral to a genetics department would be helpful in deciding this. A DNA test looking directly at the mutation in the gene may prove that someone’s disease is the result of a new fault thus occurring for the first time in him or her. Diagram and information provided by Prof Peter A Farndon, MD, FRCPReviewed and and updated 27/09/2018.