Emergomycosis – an emerging mycosis

Emergomycosis is a systemic fungal mycosis caused by a novel dimorphic fungi called Emergomyces species. It is mainly seen in immunocompromised patients. The first case of Emergomycosis was identified in 1994 in Italy; however, the fungus was described in 1998. Disseminated Emergomycosis observed a case fatality rate of 48%.

These fungi were initially classified as Emmonsia but later placed under the genus Emergomyces. The fungus in this genus are –

• Emergomyces pasteurianus (type species)
• Emergomyces africanus,
• Emergomyces canadensis,
• Emergomyces orientalis,
• Emergomyces europaeus
• Emergomyces crescens
• Emergomyces sola

The last two are not associated with disseminated fungal mycosis. Cases have been reported from Asia, Africa, Europe and North America.

Many cases have been identified in South Africa since the introduction of broad-range PCR, suggesting that many cases of Emergomycosis are possibly misidentified as Histoplasmosis. The number of Histoplasmosis cases has gone down at the same time in South Africa.

Disease process

Emergomyces exist in mould form in the soil. It releases conidia into the air, which the human inhales. Inside the human body, it transforms into the yeast phase by a temperature-dependent process. In susceptible (in this case, immunocompromised patients due to HIV, transplant, malignancy etc.) individuals may cause pulmonary and disseminated disease. The dissemination mainly occurs via the haematogenous route inside the macrophages.

Disease caused by Emergomyces-

• Widespread cutaneous disease (papules, plaques, nodules, or ulcers)
• Pulmonary disease (reticulonodular disease, consolidation, effusion)
• Lymphadenopathy
• It may also affect the gastrointestinal tract, liver, lymph nodes, and bone marrow.

Diagnosis

Sample – biopsy of affected tissue, sputum, BAL, bone marrow aspirate etc

Histology	It grows on Saboroud agar at @24-30 degrees C. Yellow/White/tan glabrous colony that becomes slightly raised, powdery and furrowed at a later stage. Reverse – Ochre-buff The yeast phase can be seen when incubated at 35 degrees C on malt extract agar/potato dextrose agar.
Culture	No sensitive and specific serological tests. The cross reaction has been seen with Histoplasma galactomannan urine antigen test or 1,3-β-D-glucan test.
Microscopy	Slender conidiophores arise from the hyphae at a right angle. form “florets” of short secondary conidiophores bearing single small subspherical conidia
PCR	Gold-standard
Serodiagnosis	No sensitive and specific serological tests. The cross-reaction has been seen with Histoplasma galactomannan urine antigen test or 1,3-β-D-glucan test.

Treatment

Based on observational studies –

Amphotericin B for 10–14 days (pref liposomal preparation) followed by
Itraconazole or another newer azole for 12 months pending immune reconstitution.
(Fluconazole should be avoided).
Lifelong suppression may be required if the immunosuppressed state persists.

Ref:

Schwartz et al., Emergomyces: The global rise of new dimorphic fungal pathogens, PLOS Pathogens, September 19, 2019, https://doi.org/10.1371/journal.ppat.1007977

Arghadip Samaddar and Anuradha Sharma, Emergomycosis, an Emerging Systemic Mycosis in Immunocompromised Patients: Current Trends and Future Prospects, Front. Med., 23 April 2021 | https://doi.org/10.3389/fmed.2021.670731