When being blue means being blue (literally)

Consanguineous marriages are those between closely related family members or members of a small, isolated population of people that were descended from a common ancestor. Such marriages are usually frowned upon, because it leads to an accumulation of mutations within these groups and the cluster-ing of genetic disorders. These are usually mutations in a recessive trait that requires two abnormal genes for the trait to be manifest. Family or group members who don’t exhibit the trait are more likely to be carriers of one abnormal gene, so the chances of the trait appearing in the offspring of two such members are high.

There are numerous examples of such a situation. One example, the Ashkenazi Jews, are mainly of Southern European descent. They have been present throughout history, but their population was greatly decimated during the Holocaust of the Second World War. Because of their relatively small popu-lation size and strict religious adherence to marriage within their population, 4-10% are carriers for one of several genetic disorders, including Tay-Sachs dis-ease (fatal affliction of early childhood), cystic fibrosis (incapacitating lung con-dition) and Gaucher Disease (less serious and treatable). Because of this, cou-ples are advised to seek genetic counseling.

A second example are the Pennsylvania Dutch. Another community that is isolated by geography and customs, they exhibit a higher percentage of polydactyly (6 digits on each hand) than the general population.

Which leads me to the fascinating topic of an upcoming Mt Zion book club selection, the blue people of Kentucky. Martin and Elizabeth Fugate lived in a very isolated area of the state where newcomers were rarely seen. Martin carried both mutations of a gene that resulted in a very rare genetic condition, blue skin color, and when they married in 1822, he had no idea that Elizabeth, coincidentally, carried that same rare gene. Of their seven offspring, four had blue skin, and because their offspring married cousins and other close relatives, the blue skin disorder spread between families. These individuals lived a life of shame, ostracized by others.

This small, isolated community of blue people persisted into the 20th century when, in the 1960s, the cause of their blue skin was investigated. It was determined that they suffered from a disease known as methemoglo-binemia. When methemoglobin levels in red blood cells exceed 1%, the skin turns blue, lips turn purple and the blood turns a chocolate brown color. Inter-estingly, this disease can be inherited or can be triggered by exposure to chemi-cals such as benzocaine or xylocaine.

The good news was that by simple administration of a methylene blue tablet, they were cured of their condition. They were finally free of the derision and scorn exhibited by the community and could now live a normal life.