Clinicians in Ontario should be aware of symptoms and areas where disease is endemic.

A retrospective study of 45 patients hospitalized with blastomycosis of bones or joints revealed 41 cases of osteomyelitis and 12 cases of septic arthritis. The majority were men (35 [78%] patients) and non-Aboriginal (32 [71%] patients). Median time from the onset of symptoms to hospitalization was shorter in women than men (male, 48 d; female, 14 d; P < 0.02), and shorter for Aboriginals than non-Aboriginals (non-Aboriginal, 50 d; Aboriginal, 19 d; P < 0.04). Cutaneous disease was present in 33 (73%) patients, and lung involvement was present in 29 (64%) patients. The most common osseous sites of involvement were the lower limb and axial skeleton. Common orthopaedic symptoms of bone lesions included bone pain in 42 (78%) patients, swelling in 32 (59%) patients, and soft tissue abscesses in 21 (39%) patients. Joint infection (12 patients) manifested as a monoarticular arthropathy presenting with effusion in 9 (75%) patients, pain in 8 (67%) patients, and decreased range of motion in 5 (42%) patients. Osseous blastomycosis can mimic bacterial infection and should be included in the differential diagnosis of bone and joint infection in patients who have visited or who live in geographic regions where B dermatitidis is endemic.

Blastomycosis is a cause of serious, potentially life-threatening pulmonary infection in this geographic region.

Independent risk factors for development of blastomycosis included immunosuppression for any reason (including drugs or disease), collagen vascular disease, being an outdoor worker, and having a coworker with blastomycosis. Canine blastomycosis was not a risk factor for human disease in dog owners.

Blastomycosis is a granulomatous infection caused by the thermally dimorphic fungus, Blastomyces dermatitidis, for which seasonal variation has been proposed. We conducted a retrospective review of medical records of 324 patients with blastomycosis in Manitoba and northwestern Ontario. The average age of patients at the time of diagnosis was 39+/-20 (range, 0-85) years. Symptoms referable to blastomycosis were first noted in the autumn and winter (September to February) by 63% of the patients. The seasonal distribution of cases was different for localized pulmonary infection than the disseminated disease (P<0.0001). For localized lung disease, the peak incidence of symptom onset occurred in the autumn, and lowest incidence in the spring; one half (50%) of the patients with diffuse lung disease had onset of symptoms in the spring months and a few (11%) cases occurred during the summer. We noted a distinct seasonal variation in the clinical presentation of blastomycosis. The observed pattern suggests that summer environmental exposure and acquisition of the infection results in an early (1-6 months) localized pneumonia in the majority of cases, followed by later (4-9 months) reactivation or slow progression of asymptomatic infection resulting in isolated extrapulmonary or disseminated hematogenous disease in the minority.