Blastomycosis (sometimes called North American blastomycosis or Gilchrist’ s disease) is caused by the yeastlike fungus Blastomyces dermatitidis, which usually infects the lungs and produces bronchopneumonia. Less commonly, this fungus may disseminate through the blood and cause osteomyelitis and central nervous system (CNS), skin, and genital disorders. Untreated blastomycosis is slowly progressive and usually fatal; however, spontaneous remissions occasionally occur. With antifungal drug therapy and supportive treatment, the prognosis for patients with blastomycosis is good.
B. dermatitidis is probably inhaled by people who are in close contact with the soil. The incubation period may range from weeks to months. Blastomycosis is generally found in North America (where B. dermatitidis normally inhabits the soil), and is endemic to the southeastern United States. Sporadic cases have also been reported in Africa. Blastomycosis usually infects men ages 30 to 50, but no occupational link has been found.
Initial signs and symptoms of pulmonary blastomycosis mimic those of a viral upper respiratory tract infection. These findings typically include a dry, hacking, or productive cough (occasionally hemoptysis), pleuritic chest pain, fever, shaking, chills, night sweats, malaise, anorexia, weight loss, and arthralgia. It can progress to pneumonia.
Cutaneous blastomycosis causes small, painless, nonpruritic, and nondistinctive macules or papules on exposed body parts. These lesions become raised and reddened and occasionally progress to draining skin abscesses or fistulas.
Dissemination to the bone causes soft-tissue swelling, tenderness, and warmth over bony lesions, which generally occur in the thoracic, lumbar, and sacral regions; long bones of the legs; and, in children, the skull.
Genital dissemination produces painful swelling of the testes, epididymis, or prostate; deep perineal pain; pyuria; and hematuria. CNS dissemination, which usually only occurs in immunocompromised hosts, causes meningitis or cerebral abscesses with resulting decreased level of consciousness (LOC), lethargy, and change in mood or affect. Other forms of dissemination may result in Addison's disease (adrenal insufficiency), pericarditis, and arthritis.
Diagnosis of blastomycosis requires:
❑culture of B. dermatitidis from skin lesions, pus, sputum, or pulmonary secretions
❑microscopic examination of tissue specimens from the skin or the lungs or of bronchial washings, sputum, or pus, as the physician finds appropriate
❑immunodiffusion testing, which detects antibodies for the A and B antigen of blastomycosis.
In addition, suspected pulmonary blastomycosis requires a chest X-ray, which may show pulmonary infiltrates. Other abnormal laboratory findings include increased white blood cell count and erythrocyte sedimentation rate, slightly increased serum globulin levels, mild normochromic anemia and, with bone lesions, increased alkaline phosphatase.
All forms of blastomycosis respond to amphotericin B. Ketoconazole or fluconazole may be used as alternative agents and may be more effective with the patients who are immunocompromised. Patient care is mainly supportive.
❑In severe pulmonary blastomycosis, check for hemoptysis. If the patient is febrile, provide a cool room and give tepid sponge baths.
❑If blastomycosis causes joint pain or swelling, elevate the joint and apply heat. In CNS infection, watch the patient carefully for decreasing LOC and unequal pupillary response. In men with disseminated disease, watch for hematuria.
❑Infuse I.V. antifungal agents slowly (too-rapid infusion may cause circulatory collapse). During infusion, monitor vital signs (temperature may rise but should subside within 1 to 2 hours). Watch for decreased urine output and monitor laboratory results for increased blood urea nitrogen and creatinine levels. Monitor serum potassium levels for signs of amphotericin B-induced hypokalemia, which may indicate renal toxicity. Report any hearing loss, tinnitus, or dizziness immediately. To relieve the adverse effects of amphotericin B, give anti-emetics and antipyretics, as ordered.
Review other book chapters online related to Blastomycosis:
Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Professional Guide to Diseases (Eighth Edition) Authors: Springhouse Publisher: Lippincott Williams & Wilkins Copyright: 2005 ISBN: 1-58255-370-X 
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