A few of our family members are heterozygous for rs13078881. Enlis puts the Allele Frequency at 3.17%. Many of the studies regarding this mutation are focused on the homozygous mutation population and Biotindase deficiency. My focus as the caretaker for 5 of us with CFS is to make sure we get everyone in our family with CFS to be at their best by tweaking items within our control to see if such tweaks help with the symptoms. The interesting thing for heterozygotes of this mutation is not that they are considered carriers of a biotinidase deficiency mutation, but that there is a known significant loss of the enzyme (SNPedia has articles placing the mutation with 48% of normal enzyme activity and 52% loss of enzymatic activity). https://www.snpedia.com/index.php/Rs13078881 So while people may view this genetic mutation as requiring two copies to be detrimental, this mom saw an opportunity to make sure the carriers in our family were taking biotin supplements. It only takes a tiny amount of biotin to reach the recommended daily allowance. I’m not one for overdoing vitamins and supplements. I haven’t given biotin to those without this mutation. Biotin is a water soluble B vitamin. In our very un-scientific study of family members, the family members with this mutation believe the little supplements of biotin a day are providing a step up in energy levels and a reduction in muscle weakness. There are many flaws in this at home study, one being that each individual knew they were being given the supplement. Could there have been a mental kick for them – maybe? But in a family of CFS, I’ll take the uptick either way. Of course, had there been any issues with the biotin supplements, it would have been stopped immediately.