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Microbiology · Dimorphic fungi

Paracoccidioides brasiliensis !

  • Fungus
  • Exam priority: medium

A dimorphic soil fungus of rural and coffee-growing areas; it causes mouth ulcers, chronic lung damage and sometimes adrenal insufficiency.

Updated 2026-11-01

Also called: Paracoccidioides lutzii, South American blastomycosis

At a glance

Shape
Large yeast with many small buds spread around the whole cell
Family
Ajellomycetaceae (Onygenales)
Type
Thermally dimorphic fungus: mold in soil, yeast in tissue
Stain
KOH on sputum or scrapings; silver (GMS) and PAS on biopsy
Size
Large yeasts, up to about 30 µm

Morphology

  • In the environment and at room temperature: mold with conidia
  • In tissue: a large thick-walled mother cell
  • Several small buds sprout at once all around its edge, so the cell looks like a spoked wheel or a ship's helm seen face on

Transmission

  • Inhaling conidia from soil during farm work
  • Rarely by direct inoculation of skin or oral mucosa
  • Not spread from person to person

Reservoir: Soil of humid tropical and subtropical farmland; Armadillos (possible reservoir)

Isolation precautions

What the care team adds to standard precautions.

  • Standard

Virulence factors

  • Conversion to yeast at body temperature; estrogens block this step, which helps explain why the adult form is far more common in men
  • Survival inside macrophages and a granulomatous response with fibrosis
  • Wall antigens (glycoprotein gp43) that modulate the immune response

Diseases it causes

  • Paracoccidioidomycosis: chronic adult form (lungs and mucosa) and acute or juvenile form (lymph nodes, liver, spleen and marrow) Paracoccidioidomycosis →

Clinical picture

  • Mouth and lip ulcers with a granular base and pinpoint bleeding, which can mimic cancer
  • Lung infiltrates and fibrosis, worse with smoking
  • Large neck lymph nodes that may drain
  • Adrenal insufficiency in disseminated disease

Diagnosis

  • KOH on sputum, ulcer scrapings or pus: the multiple-budding yeast is diagnostic
  • Biopsy with silver (GMS) or PAS
  • Culture, slow
  • Serology (immunodiffusion) for support and follow-up; P. lutzii can give false negatives with P. brasiliensis antigens

Treatment

Azoles (itraconazole) for mild and moderate disease; trimethoprim-sulfamethoxazole as an alternative; amphotericin B for severe disease, followed by an azole. Treatment is long.

Drug class only; doses and regimens are set by the clinician from the current guideline.

In Pharmacology:

Prevention

  • No vaccine
  • Stopping smoking reduces lung damage
  • Early diagnosis in rural workers with chronic mouth ulcers

Test yourself

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

What does Paracoccidioides look like in tissue or on KOH?

A large thick-walled yeast with many small buds sprouting all around its edge, like a ship's helm.

Why is adult paracoccidioidomycosis far more common in men?

Estrogens inhibit the mold-to-yeast conversion; farm-work exposure also plays a part.

Which endocrine complication is sought in disseminated paracoccidioidomycosis?

Adrenal insufficiency.

In what kind of Colombian areas is paracoccidioidomycosis concentrated?

In humid rural areas, mainly coffee-growing ones, in Antioquia, Santander, Valle, Huila, Nariño and the Coffee Axis.

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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: Thinking in paracoccidioidomycosis: a delayed diagnosis of a neglected tropical disease, case report and review of clinical reports and eco-epidemiologic data from Colombia since the 2000 (BMC Infectious Diseases (PMC, NLM), 2020); Paracoccidioidomycosis: Current Status and Future Trends (Clinical Microbiology Reviews (PMC, NLM), 2022).

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Representative model, for educational purposes only.