Emergomycosis

Published 18.11.21

Emergomycosis is a systemic fungal mycosis caused by a novel dimorphic fungi called Emergomyces species. It is mainly seen in immunocompromised patients. Although the first case of Emergomycosis was identified in 1994 in Italy, the fungus was described in 1998.

Disseminated Emergomycosis has a case fatality rate of 48%.

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

• Emergomyces pasteurianus (type species)

• Emergomyces africanus,

• Emergomyces canadensis,

• Emergomyces orientalis,

• Emergomyces europaeus

• Emergomyces crescens

• Emergomyces sola

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 cases of Emergomycosis were possibly misidentified as Histoplasmosis. The number of Histoplasmosis cases has gone down at the same time in South Africa.

(click on the image to see a high-resolution image.

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.

Emergomyces can cause -

• Widespred 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

Samples that could be tested – biopsy of affected tissue, sputum, BAL, bone marrow aspirate etc.

Histology

• May not be able to distinguish it from Histoplasma.

• Chronic granuloma, intracytoplasmic narrow-based budding yeasts, giant cells.

Culture

• It grows on Saboroud agar @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.

Microscopy

• Slender conidiophores arise from the hyphae at a right angle.

• It forms “florets” of short secondary conidiophores bearing single small subspherical conidia.

PCR

• Gold-standard

Serodiagnosis

• No sensitive and specific serological tests.

• Cross reaction has been seen with Histoplasma galactomannan urine antigen test or 1,3-β-D-glucan test.

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.

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