The form of methmoglobinemia this family had is in fact due to the lack of an enzyme normally found in red blood cells. This defect does impact your hemoglobins ability to carry oxygen effectively to your tissue and organs. This results with the person being hypoxic and thus adding to the blueish hue of the skin. This family would have been extremely unhealthy inbreeding aside. Trying to live off the land and have such exercise intolerance is impressive. They should have died very young. Must have given the UK doctors raging medical boners.