Blastomycosis is a fungal infection caused by Blastomyces dermatitidis .This dimorphic organism can grow in either a yeast or as a mycelial form. The organism is found as a normal inhabitant of soil; therefore, the highest incidence of this infection is found in agricultural workers, particularly in the middle Atlantic and southeastern portions of the United States. This geographic distribution of the infection has led to the designation by some as “North American blastomycosis.” Infection by the same organism, however, has also been found in Mexico and Central and South Americas.
Infection with Blastomyces begins in a vast majority of cases by inhalation; this causes a primary pulmonary infection. Although an acute self-limiting form of the disease exists, the infection commonly follows a chronic course beginning with mild symptoms such as malaise, low-grade fever, and mild cough. If the infection goes untreated, the symptoms worsen to include shortness of breath, weight loss, and production of blood-tinged sputum. Infection of the skin, mucosa, and bone may also occur, resulting from metastatic spread of organisms from the pulmonary lesions through the lymphatic system. The skin and mucosal lesions start as subcutaneous nodules and progress to well-circumscribed indurated ulcers.
ORAL MANIFESTATIONS
Oral lesions are rarely the primary site of infection. When oral lesions have been reported as a first sign of blastomycosis, they have occurred in patients with mild pulmonary symptoms that have been overlooked by the patient or physician. Most cases of oral involvement demonstrate concomitant pulmonary lesions on chest radiographs.
The most common appearance of the oral lesions of blastomycosis is a nonspecific painless verrucous ulcer with indurated borders, often mistaken for squamous cell carcinoma. Occasionally, this mistake is perpetuated by an inexperienced histopathologist who confuses the characteristic pseudoepitheliomatous hyperplasia with malignant changes.
Other oral lesions that have been reported include hard nodules and radiolucent jaw lesions. Page and colleagues reported two cases of painless oral mucosal ulcers as the first sign of blastomycosis; in both cases, a careful history taking revealed mild respiratory symptoms.Bell and colleagues reported 7 cases of oral lesions occurring in patients with blastomycosis; 4 presented as chronic oral ulcers and 3 as radiolucent bone lesions.216
Chest radiographs showed concomitant pulmonary involvement in all cases.
Dentists should include the diagnosis of blastomycosis in the differential diagnosis of a chronic oral ulcer. The diagnosis cannot be made on clinical grounds alone. The index of suspicion should increase when a chronic painless oral ulcer appears in an agricultural worker or when the review of systems reveals pulmonary symptoms. Diagnosis is made on the basis of biopsy and on culturing the organism from tissue.
The histologic appearance shows pseudoepitheliomatous hyperplasia with a heavy infiltrate of chronic inflammatory cells and microabscesses.
TREATMENT
Treatment for blastomycosis is similar to that described for histoplasmosis.