Thanks very much, Kiwi. I will try to do some digging on all this.

As coincidence would have it, Dr. Wolf called right as I was reading your post. He said my results indicate I am not biotinidase deficient, but cannot rule out the possibility that my lower levels are not playing a role in my problems. They are just not at a level that would be known to cause specific issues seen with biotinidase deficiency as it's defined.

They have a paper coming shortly on adults with undetected deficiency and the symptoms that presented later in life...optic neuropathy, muscle weakness and limb paresthesia. He said they were losing their vision, and had immediate reversal of all their symptoms upon starting biotin supplements. Oh, if only...