Vol. 16, No. 34
THE JOHNS HOPKINS MICROBIOLOGY NEWSLETTER
Monday, September 8, 1997
A. Provided by Carmela Groves, R.N., M.S., Chief, Division of Outbreak Investigation, Maryland Department of Health and Mental Hygiene
No information provided this week.
B. The Johns Hopkins Hospital: Information provided by David Taylor, M.D., Pathology
Clinical Information: The patient is a 38 yr. old black female with a history of sarcoidosis who developed papulopustular lesions along the nasal canthas region. The patient was otherwise asymptomatic. The lesions did not resolve with steroid injection and increased in size and number. A chest x-ray showed bilateral hilar adenopathy similar to that seen in a chest x-ray from 1995.
A skin biopsy was performed and showed hyperkeratosis, acanthosis, granulomatous inflammation and rare broad based budding yeast consistent with North American Blastomycosis.
North American Blastomycosis
Blastomycosis is a systemic infection caused by the thermally dimorphic fungus Blastomyces dermatitidis. Previously this mycosis was thought to be restricted to North America, but in recent years autochthonus cases have been diagnosed in Africa, the Middle East, Asia and Europe. The vast majority of cases however originate in North America. In the United States, blastomycosis is endemic in the Mississippi River Basin, around the Great Lakes and in the Southeast. Synonyms include North American blastomycosis, Chicago disease and Gilchrist's disease.
Epidemiology: Clinical and epidemiologic studies indicate that humans and animals usually contact blastomycosis after inhaling aerosolized infectious conidia of the mycelial form of the fungus growing as a saprophyte in the soil and the primary focus of the infection is in the lungs. Most primary pulmonary infections are asymptomatic or mildly symptomatic but self-limited in immunocompetent hosts. Primary cutaneous infections are rare and usually caused by accidental inoculation of the fungus into the skin and subcutaneous tissues. The disease is usually sporadic, and is more frequent in persons 30 to 50 years of age who are often outdoors. Epidemics of blastomycosis are rare, affect all ages and both sexes and are usually related to a point-source exposure. Of the domestic animals, dogs are most susceptible; the infection rate is estimated to be 10 times that for humans.
Clinical Features: The two major clinical forms of blastomycosis are cutaneous and systemic. Both forms have a pulmonary inception, but their clinical presentation, course, pathologic features and prognsosis differ. Patients with the cutaneous form of blastomycosis present with a papular, pustular, or indolent, ulcerative-nodular and verrucous skin lesions with crusted surfaces and raised, serpinginous borders. Lesions are usually painless, do not itch and are often on exposed parts of the body, particularly the face, neck, and hands. In cutaneous blastomycosis, primary pulmonary lesions are usually inapparent, systemic symptoms are absent or mild and the general health of the patient is not impaired. If left untreated, the clinical course of cutaneous blastomycosis can range from months to years, with remissions and exacerbations and progressive increase in the size of lesions. The rare primary cutaneous lesions of blastomycosis are localized, self-limited infections that are accompanied by regional lymphadenopathy and almost never disseminate.
Systemic blastomycosis begins in the lung and remains confined to the lung or disseminates hematogenously to other organs, particularly skin, larynx, bones and joints, male genitourinary tract especially the prostate), central nervous system, lymph nodes, heart and adrenal glands. Overwhelming primary infection with B. dermatitis can cause severe diffuse pneumonitis and adult respiratory distress syndrome, even in immunocompetent patients. Untreated systemic infections are often severe, progressive, and fatal; the mortality rate is greater than 90%. Patients usually present with chronic respiratory symptoms, including productive cough, dsypnea, low-grade fever, night sweats and weight loss. Concomitantly, about two thirds of patients have skin lesions, one third have bone lesions and one fifth of male patients have lesions of the genitourinary tract.
Like most other fungal infections, severely immunodeficient patients are at increased risk for blastomycosis. The clinical presentation is similar to that of immunocompetent patients. However infection tends to disseminate more often (especially to the central nervous system) and is more rapidly progressive in patients who are immunodeficient. Unlike cryptococcosis and histoplasmosis capsulati, blastomycosis is seldom encountered as an opportunistic mycosis in patients with AIDS or other profound cell-mediated immunodeficiencies.
Diagnosis: Definitive diagnosis requires growth of the organism from clinical specimens which may take 5-8 weeks for detection. Because B. dermatitidis is dimorphic, it produces nonencapsulated yeastlike cells in host tissues and in vitro at 37 C on enriched media, and white-to-tan, downy-to-fluffy moulds at room temperature on standard mycologic media. A presumptive diagnosis may be made by visualization of the characteristic yeast in pus, sputum, secretions and histopathologic sections. The yeast are spherical, hyaline, 8-15 microns in diameter, multinucleated, and have vacuolated cytoplasm and thick "double-contoured walls. The yeast reproduce by budding, and the buds (blastoconidia) are attached to their parent cell by large (4-5 microns) bud pores.
Treatment: Amphotericin B is the drug of choice for severe, life-threatening blastomycosis; 2-hydroxystilbamidine, either alone or in combination with amphotericin B, also has been successfully used. The azole antifungal agents ketoconazole and itraconazole may be effective in patients who are not seriously ill, and these antifungals can be used when toxicity precludes the use of amphotericin B. Surgical excision of localized lesions may be a valuable adjunct to antifungal therapy.
References:
1. Chandler, FW. Blastomycosis in Conner DH, Chandler FW eds. Pathology of Infectious Disease. Stamford, Conneticut, Appleton and Lange; 1997:943-951.
2. Chapman, SW. Blastomyces Dermatitidis in Mandel GL, Bennett JE and Dolin R eds. Principles and Practice of Infectious Diseases, 4th edition, vol 2. New York, Churchill Livingstone; 1995:2353-2365.
3. Myer KC, McManus EJ, Maki DG. Overwhelming pulmonary blastomycosis associated with the adult respiratory distress syndrome. N Engl J Med 1993;329:1231-1236