Emmonsiosis, also known as emergomycosis, is a systemic fungal infection that can affect the lungs, generally always affects the skin and can become widespread. ^{[1] [2]} The lesions in the skin look like small red bumps and patches with a dip, ulcer and dead tissue in the centre. ^[4]

It is caused by the Emergomyces species, a novel dimorphic fungus, previously classified under the genus Emmonsia. ^[3] These fungi are found in soil and transmitted by breathing in its spores from the air. ^[1] Inside the body it converts to yeast-like cells which then cause disease and invade beyond the lungs. ^[1] Diagnosis is by skin biopsy and its appearance under the microscope. ^[5] It is difficult to distinguish from histoplasmosis. ^{[3] [6]} Treatment is usually with amphotericin B. ^[3]

Emmonsiosis can be fatal. ^[3] The disseminated type is more prevalent in South Africa, particularly in people with HIV. ^[3]

Signs and symptoms

Generally, all cases have involvement of the skin. ^[5] The lesions look like small red bumps and patches with a dip, ulcer and dead tissue in the centre. ^[4] There may be several lesions and their distribution can be widespread. ^[1] The lungs may be affected. ^{[3] [4]}

Cause

It is caused by the Emergomyces species, a novel dimorphic fungus, previously classified under the genus Emmonsia. ^{[3] [7]} Following a revised taxonomy in 2017 based on DNA sequence analyses, five of these Emmonsia-like fungi have been placed under the separate genus Emergomyces. ^[3] These include Emergomyces pasteurianus, Emergomyces africanus, Emergomyces canadensis, Emergomyces orientalis and Emergomyces europaeus. ^{[3] [8]}

Emergomyces africanus was previously known as Emmonsia africanus, which has similar features to Histoplasma spp. and the family of Ajellomycetaceae. ^[6]

The disease has been observed among people who have a weakened immune system and risk factors include HIV, organ transplant and steroid use. ^{[1] [3]}

Mechanism

The fungus is found in soil and is released in the air. ^[1] Transmission is by breathing in fungal spores from the air. ^[1] Inside the body it converts to yeast-like cells which then cause disease and invade beyond the lungs. ^[1] In people with HIV, Emmonsiosis has been associated with Immune reconstitution inflammatory syndrome following initiating antiretroviral treatment. ^[1]

Diagnosis

Diagnosis is by skin biopsy and its appearance under the microscope. ^[5]

Differential diagnosis

Generally, it is difficult to distinguish from histoplasmosis. ^[6] Other conditions that appear similar include tuberculosis, ^[5] blastomycosis, sporotrichosis, chicken pox, Kaposi's sarcoma and drug reactions. ^[4]

Treatment

Treatment usually includes amphotericin B. ^[3]

Prognosis

It can be fatal. ^[5]

Epidemiology

The disseminated type is more prevalent in South Africa, particularly in people with HIV. ^[5]

History

The disease was thought to be a rare condition of the lung. ^[2] Early cases may have been misdiagnosed as histoplasmosis. ^[6]

Other animals

The genus Emmonsia can cause adiaspiromycosis, a lung disease in wild animals. ^[9]

References