Spina Bifida Hereditary and Genetics
Often one of the questions family members of the patient with spina bifida will ask “Why us?” “What is the cause of my condition?” “Is my condition genetic and can I pass it on if I have children?”
These are all valid and understandable questions. The problem is that scientists are not yet able to answer the heritability questions about spina bifida yet. There seems to be a definite genetic link and the fact that in at least 70% of the cases the absence of folate seems to play a huge role suggest a genetic metabolic link, but the entire picture of genetics has not yet emerged.
It is clear that in the general population, the chance of a child having spina bifida is about 0.1 – 0.2% worldwide. If a woman has already had a child with spina bifida, the chance of having another affected child is 1 in 20. The chances are also increased if a woman’s close blood relative has had a child with spina bifida. A woman who has spina bifida is also at higher risk of having a spina bifida child. It seems that only 5% of the cases involve direct hereditary effects, however. So a woman who has spina bifida has about a 1 – 5% chance of having a spina bifida child and that increases to 15% if both parents have spina bifida. This is clearly more complex a condition than one that is directly passed down from the parents.
More recently, specific genes that seem to be linked to this neural tube defect have been discovered. Since spina bifida is a heterogeneous disease, it is likely that several genes will be involved or that an entire metabolic pathway is affected in various ways.
A study looking at the DNA of 1500 children with the condition and their parents found that a group of genes involved in glucose metabolism seem to have some sort of link to those who are born with spina bifida. In addition, the gene mthfr also seems to be involved in at least some of the spina bifida cases.
MTHFR is a gene that codes for a protein important in folic acid (vitamin B9) metabolism. Another folate-related gene, SHMT1, is altered in some patients. The VANGL1 gene which encodes part of glucose metabolism seems to be a variant that is not directly related to folate processing. Depending on the race of the child, some genes seem to be more affected than others. Hopefully we will be able to genetically test parents and children to determine the risk of spina bifida and hopefully control it before any damage is done.
Dr. Margo Whiteford on Spina Bifida and Genetics