Blastomycosis, north americanB40.3

Chronic, deep systemic mycosis with primary lung infection (by inhalation of the pathogens), occurring mainly in North America (Mississippi basin, east and south of the USA). Haematogenous scattering leads to secondary involvement of multiple organs including the skin. Occurs also as an opportunistic infection in various diseases. Basic diseases.

Blastomyces dermatitidis (called Ajellomyces dermatitidis in the sexual stage), is a dimorphic fungus that can grow as a yeast and mould. Infections occur in humans and animals (Ditmyer H et al. 2011). In humans, infection usually occurs through inhalation of spores present in the soil. Very rarely, e.g. in the case of injuries in laboratories, infection is possible by penetration of the pathogen into the skin (so-called inoculation blastomycosis).

The fungus is endemic in parts of eastern North America, particularly northern Ontario, southeastern Manitoba, Quebec south of the St. Lawrence River, parts of the U.S. Appalachian Mountains and interconnected eastern mountain ranges, the western shore of Lake Michigan, the state of Wisconsin and the entire Mississippi Valley, including the valleys of some major tributaries such as the Ohio River. In addition, Blastomyces dermatitidis is rare in Africa both north and south of the Sahara desert, as well as on the Arabian Peninsula and the Indian subcontinent. Human-to-human transmission has only been reported in very few cases.

• After an incubation period of 1-3 weeks symptoms of pulmonary infestation: cough, sputum, irregular fever, emaciation. Asymptomatic courses in about half of the cases.
• Subsequently, further organ involvement through haematogenic scattering:
  • Skin lesions (80% of cases): Preferably on the extremities and face single or multiple, ulcerated, granulomatous papules with a verrucous-crustose surface as well as larger nodules with a tendency to ulceration, reaching into the subcutis. Progressing along the edges and central healing results in arched, flat, granulomatous, purulent plaques with raised edges.
  • Rare osteomyelitis of the trunk skeleton, skull and long tubular bones.
  • Infestation of the male reproductive organs.
  • Infestation of the mucous membranes of the mouth and nose.
  • Infestation of the CNS and the urogenital system.
  • In inoculation blastomycosis (direct inoculation of the pathogen when the skin is injured), formation of a solitary ulcer surrounded by a rough edge with accompanying lymphangitis.

Microscopic and cultural pathogen detection from pus, sputum or bronchial lavage, bioptic material (by multilocular sprouting of the fungus in the yeast phase formation of characteristic "steering wheel" forms).

Detection of antibodies in serum.

Possibly animal experiment.

• Amphotericin B (e.g. Amphotericin B) i.v. 1 mg/kg bw/day over 4-6 weeks or liposomal amphotericin B (e.g. AmBisome®) initial 1 mg/kg bw i.v.; if necessary, increase gradually to 3 mg/kg bw i.v.
• Alternatively: Fluconazole (e.g. Diflucan 50) 1 cps/day for 10 weeks (less toxic). Surgical removal of abscesses, removal of necrotic tissue.
• Alternatively itraconazole for a longer period of time.

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2. Bradsher RW et al (2003) Infect Dis Clin North Am 17: 21-40
3. Ditmyer H et al (2011) Mycotic mastitis in three dogs due to Blastomyces dermatitidis. J Am Anim Hosp Assoc 47:356 - 358.
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11. Wilkerson A et al (2003) Sweet's syndrome-like blastomycosis. Am J Dermatopathol 25: 152-154
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