CHILDREN born with a particular form of spina bifida may have inherited the disorder from their maternal grandparents. This unusual finding comes from a new Irish Italian survey of the incidence of spina bifida and other neural tube defects (NTDs).
Dr Julianne Byrne, director of the Boyne Research Institute and the person who led the scientific study, told The Irish Times that the finding was significant because this was the first time that a specific type of NTD had been traced to grandparents, and the mother's side of the family seemed to be more important than the father's.
NTDs, including spina bifida, arise when an embryo's neural tube which later develops into the brain and spinal cord fails to close. The severity of the condition varies considerably some adult cases are only detected using x-rays but most affected infants die at birth.
The incidence in Ireland has traditionally been high and, although it has fallen in recent years, possibly because more foods are now supplemented with vitamins, it is still higher than elsewhere in Europe (1.5 cases per 1,000 here, compared with one per 1,000 in Italy, for example).
Doctors have suspected for some time that there was a genetic component, particularly because women who have had one NTD infant were 10 times more likely to have another one.
However, when covered that 75 per cent * births could be prevented if the mother took a folic acid ment at the time of the emphasis has been on factors.
It is still not clear why folic acid is important, but last autumn scientists were among those discovered that a mutation in ones of the folic acid genes (MTHF reductase) was associated with 13 per cent of NTDs.
The new study is part of a major survey comparing the incidence of NTDs in Ireland with Italy. The survey involved 300 Italian families and examined a type of NTD known as "high spinal lesion" which accounts for 10 per cent of cases there.
Researchers found that, even though the incidence in Italy was low, there was still a major genetic component involved. They also found that close relatives of affected children were 14 more likely to have a neural tube defect themselves.
Finally, but most unusually, it discovered that the maternal grandparents had fewer children at longer intervals than the paternal grandparents (that is, the mothers on average came from smaller families than the fathers).
According to Dr Byrne, this could be because the maternal grandmothers had spontaneous miscarriages, possibly because of a NTD pregnancy. This possible genetic link was now being investigated by the Italian scientists, she said, who were using blood samples to search for a genetic mutation.
If one is found, it could mean that a diagnostic test would one day become available for at least this type of NTD.
Dr Peadar Kirke, an epidemiologist with the Health Research Board in Dublin and one of those working on the MTHF reductase study, said he believed there was a strong genetic component to NTDs.
Dr Byrne's finding, and the link to the maternal grandparents, was "interesting and it merits further work," he said. But he cautioned against drawing conclusions on the basis of a survey, rather than genetic studies.
Dr Byrne said that the genetic studies were now beginning, as were the surveys of Irish families (both in Louth/Meath and Northern Ireland). The results of the Italian study will be published in the next issue of the American Journal official Genetics.
The Boyne Research Institute, Drogheda, is an independent research facility which specialises in studying birth defects. The Irish Italian study was funded by the institute, the Italian government, and the Italian partners, Gaslini Institute, Genoa.