Basidiobolomycosis
Basidiobolus ranarum: causative organism
Specialty	Infectious disease[1]
Symptoms	Firm painless nodule in skin,[2] tummy upset[3]
Complications	Spread to local structures[2]
Usual onset	Gradual/slow[2]
Causes	B. ranarum[2]
Diagnostic method	Medical imaging, biopsy, microscopy, culture, histopathology[2]
Differential diagnosis	Inflammatory bowel disease[2]
Treatment	Antifungals, surgery[4]
Medication	Amphotericin B[4]
Frequency	Rare[3]

Basidiobolomycosis is a fungal disease caused by Basidiobolus ranarum.^[1][5] It may appear as one or more painless firm nodules in the skin which becomes purplish with an edge that appears to be slowly growing outwards.^[3][5] A serious but less common type affects the stomach and intestine, which usually presents with abdominal pain, fever and a mass.^[3]

B. ranarum, can be found in soil, decaying vegetables and has been isolated from insects, some reptiles, amphibians, and mammals.^[2] The disease results from direct entry of the fungus through broken skin such as an insect bite or trauma, or eating contaminated food.^[1][3] It generally affects people who are well.^[2]

Diagnosis is by medical imaging, biopsy, microscopy, culture and histopathology.^[2] Treatment usually involves amphotericin B and surgery.^[3][4]

Although B. ranarum is found around the world, the disease Basidiobolomycosis is generally reported in tropical and subtropical areas of Africa, South America, Asia and Southwestern United States.^[3] It is rare.^[3] The first case in a human was reported from Indonesia in 1956 as a skin infection.^[4]

Signs and symptoms

Basidiobolomycosis may appear as a firm nodule in the skin which becomes purplish with an edge that appears to be slowly growing outwards.^[3][5] It is generally painless but may feel itchy or burning.^[3][5] There can be one lesion or several, and usually on the arms or legs of children.^[5] Pus may be present if a bacterial infection also occurs.^[3] The infection can spread to nearby structures such as muscles, bones and lymph nodes.^[2]

A serious but less common type affects the stomach and intestine, which usually presents with tummy ache, fever and a lump.^[3][6] Lymphoedema may occur.^[3][4]

Mechanism

Basidiobolomycosis is a type of Entomophthoromycosis, the other being conidiobolomycosis, and is caused by Basidiobolus ranarum, a fungus belonging to the order Entomophthorales.^[2] B. ranarum has been found in soil, decaying vegetables and has been isolated from insects some reptiles, amphibians, and mammals.^[2] The disease results from direct entry of the fungus through broken skin such as an insect bite or trauma, or eating contaminated food.^[1][3] Diabetes may be a risk factor.^[3] The exact way in which infection results is not completely understood.^[3]

Diagnosis

Diagnosis is by culture and biopsy.^[4]

A review in 2015 showed that the most common finding on imaging of the abdomen was a mass in the bowel, the liver, or multiple sites and bowel wall thickening. Initially, many were considered to have either a cancer of the bowel or Crohns disease.^[7][8]

Treatment

Treatment usually involves itraconazole or amphotericin B, combined with surgical debridement.^[4] Bowel involvement may be better treated with voriconazole.^[2]

Epidemiology

The condition is rare but emerging.^[3] Men and children are affected more than females.^[3] The disease is generally reported in tropical and subtropical areas of Africa, South America, Asia and several cases in Southwestern United States.^[2][3]

History

The first case in a human was reported from Indonesia as a skin infection in 1956.^[4] In 1964, the first case involving stomach and intestine was reported.^[4]

Society and culture

Cases among gardeners in Arizona, US, may indicate an occupational hazard, but is unproven.^[4]

Other animals

Basidiobolomycosis has been reported in a dog.^[9]