Basidiobolus ranarum

Basidiobolus ranarum is a microscopic fungus in the order Entomophthorales.

Life history
It produces large, spherical, asexual spores that are forcibly discharged. Those spores can germinate directly to produce hyphae. When they land in an unfavorable location, they can alternately germinate to produce a long, slender capilliconidiophore that bears a single, falcate capilliconidium. At the distal tip of the capilliconidium is a sticky mucous drop that is presumed to aid in dispersal. B. ranarum can also produce thick-walled resting spores that are presumably the sites of meiosis.

B. ranarum can be isolated from decaying leaf litter and the excrement of frogs and terrestrial, insect-eating reptiles. It has been considered a commensal of frogs, although there is no evidence that it multiplies or persists in a frog's gut. It can be a human pathogen, causing a disease called basidiobolomycosis (formerly entomophthoromycosis).

Basidiobolomycosis
Basidiobolomycosis is a rare disease caused by the fungus Basidiobolus ranarum, member of the class Zygomycetes, order Entomophthorales, found worldwide. Usually basidiobolomycosis is a subcutaneous infection but it has been associated with gastrointestinal disease.

Clinical features
Basidiobolomycosis is usually a superficial infection of skin, but may very rarely cause lesions of the bowel or liver, mimicking bowel cancer, or Crohn's disease. In patients with deep involvement, the eosinophil count may be raised, falsely suggesting a parasitic infection.

Diagnosis
Diagnosis is by laboratory culture of the organism, usually from pieces of tissue taken from the patient. It grows easily on most media, but risks being discarded as irrelevant or being reported as a contaminant because laboratory staff are unfamiliar with it.

Diagnosis is often difficult because it is a rare disease and therefore often not recognised. The lesions often look like tumours rather than infection, so often no sample is sent for microbiology, however, the histopathology is characteristic: the Splendore-Hoeppli phenomenon describes the presence of fungal hyphae (which may exist only as ghosts on the slide) surrounded by eosinophilic material.

Treatment
Treatment for skin lesions is traditionally with potassium iodide, but itraconazole has also been used successfully.