Background:

Porphobilinogen could act as a phototoxin, a neurotoxin, and a metabotoxin.

Porphobilinogen can act as a phototoxin, a neurotoxin, and a metabotoxin. A phototoxin leads to cell damage upon exposure to light. A neurotoxin causes damage to nerve cells and nerve tissues. A metabotoxin is an endogenously produced metabolite that causes adverse health effects at chronically high levels[1].

[1]. Winkelman JW, et al. Neurotoxicity of tetraphenylporphinesulfonate TPPS4 and its relation to photodynamic therapy. Photochem Photobiol. 1987 Nov;46(5):801-7.