Paxillus

Paxillus is a genus of fungi in the family Paxillaceae. Characterized by their brown to ochre-brown colors and decurrent gills that are easily separable from the cap, Paxillus species are generally found growing on wood or soil. The genus has a global distribution, and species within Paxillus can be difficult to identify to species level without microscopic examination.

A key feature of Paxillus is that the gills bruise brown when handled. The spore print is typically brown.

Some Paxillus species are known to cause serious poisoning. Notably, Paxillus involutus was once considered edible but is now known to cause autoimmune hemolytic anemia in susceptible individuals, leading to potentially fatal reactions after repeated consumption. Antibodies develop against the mushroom and then also attack red blood cells. Because of this, all Paxillus species should be regarded as potentially poisonous and avoided for consumption.

Research into the taxonomy and phylogeny of Paxillus continues, with ongoing efforts to clarify species boundaries and relationships within the genus. The use of molecular techniques, such as DNA sequencing, has been instrumental in resolving taxonomic uncertainties.