My paternal grandmother, Janet Armour Fleming, maintained that, via her mother Margaret Armour, she was related to the Jean Armour beloved of Robert Burns, which statement I took with a pinch of salt. My scepticism increased when an uncle provided me with a simple Fleming – Armour family tree of four generations of names, dates and places, and which subsequent research showed to contain at least six errors! However, a genetically-linked illness now suggests that grandmother may have been right.
Cystic fibrosis (CF) occurs when a child inherits a defective gene from both parents. This gene pair gives rise to the condition, which causes severe problems in the lungs and digestive system. Sufferers always used to die in infancy, but even nowadays, despite enormous advancements in medicine and genetic understanding, they rarely live beyond their early thirties. Two of the three children of a paternal cousin died of CF at twenty-one, one awaiting a heart-lung transplant and the other shortly after the operation.
The recessive CF gene can be passed down unnoticed in a family for generations: carriers are as healthy as anyone else. However, when two carriers have children, for each pregnancy there is a one-in-four chance that the child will inherit both defective genes:
Every child of a carrier has a one-in-two chance of also being a carrier. The chances for grandchildren of a carrier inheriting the gene are one-in-four and for the great-grandchildren, one-in-eight. In the general population the probable incidence of the defective gene is one in twenty two for an individual; in one couple in five hundred, both will be carriers and therefore potential parents of CF children.
For a long time, the family had no idea which of my cousin’s parents was the carrier. Years ago, she and her husband were shown a medical genetics slide which seemed to indicate that Robert Burns and Jean Armour were carriers as several of their children died in infancy in a pattern which looked very like CF. The children Burns had with other women did not show this pattern. More recently, the cousins met an Armour from Ayrshire with CF among his relations.