‘Autosomal recessive’ means that both copies of one of the collagen VI genes are mutated. This is often caused when both parents are carriers of the condition, meaning the parents have a single mutated gene and, while they do not experience symptoms, they can pass the mutated gene on to their children. If both parents are carriers of the condition, they have a risk of 25 percent – or one in four – of passing the condition on to their children in each pregnancy.
Conditions caused by ‘autosomal dominant’ mutations require only one copy of a gene to be mutated. These mutations are often ‘de novo’, which means the genetic change occurred spontaneously in the child and is not carried by either parent.
Sometimes, cases that appear to be caused by ‘de novo mutations’ are associated with a small risk (approximately one percent) that a parent may carry the condition (via a genetic mechanism known as ‘germline mosaicism’), but this is rare. Given the complexity of genetic diagnosis and inheritance patterns, all families of children with UCMD should be referred for genetic counselling. Your neurologist or GP will be able to give you a referral for genetic counselling.