<P> Mutations in the GIF gene are responsible for a rare inheritable disease called intrinsic factor deficiency which results in malabsorption of vitamin B . </P> <P> In most countries, intramuscular injections of vitamin B are used to treat pernicious anemia . Orally administered vitamin B is absorbed without intrinsic factor, but at levels of less than one percent than if intrinsic factor is present . Despite the low amounts absorbed, oral vitamin B therapy is effective at reducing symptoms of pernicious anemia . Vitamin B can also be given sublingually, but there is no evidence that this route of administration is superior to the oral route . Despite evidence of efficacy of oral vitamin B treatment, only Canada and Sweden routinely prescribe this route of administration . </P>

What factor is activated at the beginning of the intinsic pathway