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[Microbiology](https://durgical.com/en/microbiology/) · [Fungi](https://durgical.com/en/microbiology/#d-fungus)

# Dimorphic fungi

- Fungi

Fungi that live as molds in soil and switch to yeasts inside the body; acquired by inhaling spores, they cause the endemic mycoses.

Updated 2026-11-01

## What they are

Thermally dimorphic fungi grow as molds (hyphae with conidia) in nature and at room temperature, and turn into yeasts at body temperature. Most enter through the lungs when contaminated soil is disturbed; Sporothrix enters through a skin wound. Each has its own geography and its typical look in tissue.

## What they share

- Mold in the environment (around 25 °C) and yeast in tissue (37 °C); Coccidioides forms spherules instead of yeasts
- Not spread from person to person
- Infection almost always by inhaling conidia; Sporothrix by skin inoculation
- Can stay latent and reactivate with immunosuppression

## Key points

- Rule of thumb: mold in the cold outside, yeast in the heat of the body
- Histoplasma: small yeast inside macrophages; soil with bird or bat droppings
- Paracoccidioides: large yeast with many buds around it; coffee-growing areas of Colombia
- Blastomyces: large thick-walled yeast with a single broad-based bud
- Coccidioides: spherules full of endospores; arid areas
- Sporothrix: elongated yeast in tissue; nodules climbing along the lymphatic path

## Microorganisms in this group

- [**Histoplasma capsulatum** A fungus of soil with bird or bat droppings (caves); inhaled, it spreads in advanced HIV with fever, weight loss and pancytopenia. Exam priority: high](https://durgical.com/en/microbiology/histoplasma-capsulatum/)
- [**Paracoccidioides brasiliensis** A dimorphic soil fungus of rural and coffee-growing areas; it causes mouth ulcers, chronic lung damage and sometimes adrenal insufficiency. Exam priority: medium](https://durgical.com/en/microbiology/paracoccidioides-brasiliensis/)
- [**Sporothrix schenckii** A fungus of plants and soil that enters through a thorn or splinter; it forms nodules that climb the arm along the lymphatic vessels. Exam priority: medium](https://durgical.com/en/microbiology/sporothrix-schenckii/)
- [**Coccidioides immitis** A soil fungus of the deserts of the Americas; inhaled with dust, it causes pneumonia, sometimes with skin nodules and joint pain. Exam priority: medium](https://durgical.com/en/microbiology/coccidioides-immitis/)
- [**Blastomyces dermatitidis** A fungus of moist soils near North American rivers and lakes; it causes pneumonia and warty skin lesions, sometimes bone disease too. For completeness](https://durgical.com/en/microbiology/blastomyces-dermatitidis/)

## Test yourself

Think of the answer, then tap the question to see it.

## What does it mean that a fungus is thermally dimorphic?

It grows as a mold at room temperature and as a yeast (or spherule) at body temperature.

## Which dimorphic fungus forms spherules with endospores in tissue instead of yeasts?

Coccidioides.

## By what route do most dimorphic fungi enter the body?

By inhaling conidia from soil; Sporothrix is the exception and enters through a skin wound.

## Are dimorphic fungi spread from person to person?

No. The source is the environment, so standard precautions are enough.

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Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [Clinical Overview of Histoplasmosis](https://www.cdc.gov/histoplasmosis/hcp/clinical-overview/index.html) (CDC, 2024); [Clinical Overview of Blastomycosis](https://www.cdc.gov/blastomycosis/hcp/clinical-overview/index.html) (CDC, 2024); [Clinical Overview of Valley Fever](https://www.cdc.gov/valley-fever/hcp/clinical-overview/index.html) (CDC, 2024); [Clinical Overview of Sporotrichosis](https://www.cdc.gov/sporotrichosis/hcp/clinical-overview/index.html) (CDC, 2024).

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