Palytoxin Keratitis

Palytoxin (PTX) is a large naturally occurring toxin initially isolated from zoanthids (i.e., soft corals) in the genus  and has since been found in various marine life including microalgae. PTX is a highly deadly polyhydroxylated and partially desaturated non-proteinaceous carbon backbone with a molecular weight of 2680 kilodaltons and a lethal dose (LD) of 150 ng/kg body weight in mice when given intravenously. It is among the largest nonpolymeric natural products. It was first synthesized in totality in 1994, decades after its initial discovery. The toxin is released from organelles called nematocysts, which release spiral thread-like structures with ‘barbs’ that can pierce tissue upon contact. These soft corals are often present in aquariums due to their beauty and relatively low maintenance. Though not all species are known to produce a toxin, the exact identification of the specific genus and species is often not possible; thus, all should be treated as toxic. Inhalation, ingestion, or cutaneous contact can lead to lethal systemic effects, but a small number of cases in recent years have described ophthalmic effects that range from superficial punctate epitheliopathy to bilateral corneal melt with subsequent perforation.