Pyroluria is a familial disorder which occurs with stress, where an above-average amount of a substance consisting of "kryptopyrroles" circulate in the body. The substance is harmless in itself, but high levels of these pyrrolles systemically bind with B6 and zinc, preventing the use of these essential nutrients in the brain and body.
It is viewed with skepticism by much of the medical community, however.
Could You Have Pyroluria 2015-07-18
A Pylouria Questionnaire