An emerging fungal infection of the gastrointestinal tract that mimics cancer and inflammatory bowel disease appears to be emerging in the Southwestern United States and other desert regions, according to Mayo Clinic researchers in Arizona investigating the disease. The invasive fungus, Basidiobolus ranarum, is typically found in the soil, decaying organic matter and the gastrointestinal tracts of fish, reptiles, amphibians, and bats.

Mayo researchers studied 44 cases of human gastrointestinal basidiobolomycosis reported from around the world, including 17 from Arizona, one from southern Utah and one from elsewhere in the U.S. Eight of the 44 patients died. Mayo's review of the cases is published online in the journal Clinical Infectious Diseases.

Basidiobolomycosis is usually a subcutaneous infection in the tropical and subtropical regions of the world that develops following traumatic inoculation of the fungus under the skin. The emergence of gastrointestinal involvement with Basidiobolus in arid regions has been considered unusual.

"The exact mode of acquisition of this gastrointestinal infection is unclear, although consumption of contaminated food or dirt is the favored hypothesis," says lead author H.R. Vikram, M.D., an infectious diseases physician at Mayo Clinic, where seven of the 19 U.S. cases studied were treated. "The infection is still considered so rare that no one had put together a complete description." He adds that more study needs to be done to determine how this infection is contracted, what underlying diseases might predispose patients to this infection and how best to treat it. He emphasizes that early recognition is key to successful treatment.

The first U.S. case of gastrointestinal Basidiobolus infection was reported in 1986. The CDC subsequently investigated six cases in Arizona between 1994 and 1999. This sparked the interest of researchers at Mayo Clinic in Arizona to study this infection.

Patients with this rare fungal infection had non-specific symptoms such as abdominal pain or a mass that could be felt on examination. Before a conclusive diagnosis of the fungal infection was made, most patients were thought to have an abdominal cancer, inflammatory bowel disease or diverticulitis. Surgical resection of the area of involvement and prolonged antifungal therapy successfully treated most patients.

Study co-authors include Jerry Smilack, M.D., retired; Infectious Diseases; Jonathan Leighton, M.D., and Michael Crowell, Ph.D., Gastroenterology; and Giovanni De Petris, M.D., Anatomic Pathology.