10 January 2011
ByAppeared in BioNews 590
UK researchers have identified the genetic mutation that caused an 18th-century Irish man to grow to a height of seven and a half feet. This was the result of a growth disorder called gigantism. Studies of four modern day Irish families also presenting with similar growth disorders, showed they too expressed the same genetic mutation.
'The idea initially looked quite bizarre, but as we gained more data and identified new families affected by the mutation, our findings confirmed our theory. The most important clinical aspect of our study is that it is now possible to trace down carriers of this gene in time and treat patients before they grow to be a giant', said Professor Marta Korbonits who led the study at Barts and the London School of Medicine and Dentistry.
Gigantism is caused by the excess production of growth hormones by the pituitary gland - a gland located at the base of the brain. When the disorder presents during childhood, individuals become abnormally tall as their bones grow excessively long. However when the disorder presents after adolescence, once the natural growth spurt is over, bones increase in thickness rather than length and the disorder is termed acromegaly.
The mutated gene, AIP, identified in this study was previously shown to cause approximately 20 percent of inherited pituitary gland tumours. Pituitary gland tumours result in the excessive production of growth hormones and are therefore a known cause of both gigantism and acromegaly.
Researchers analysed DNA from the teeth of the 18th-century Irish man and compared this to DNA taken from current gigantism and acromegaly patients of Irish descent. Genetic analysis showed that the mutant AIP present in both the 18th-century Irish man and living patients was inherited from a common ancestor. Further analysis estimated that this common ancestor lived approximately 1,500 years ago and that there are between 200 and 300 living descendents carrying the same mutation.
Professor Patrick Morrison of Queens University Belfast, who was also involved in the study, said that: 'The benefits to patients locally are that we now have a genetic blood test that families at risk of this condition can choose to have, which allows early detection and prevention of excessive growth'.
This study was published in the New England Journal of Medicine.