A 28 year old white male with no significant past history was referred for preoperative clearance for left foot amputation. Patient had non-healing ulcers on his left heel and ankle for 1 month with no response to antibiotics. One year prior, he had a flulike illness, hematuria and painful left testicle which resolved spontaneously except for a persistent dry cough. CXR revealed a spot on the left lung. His TB skin test was negative. The patient denied hematospermia, weight loss, night sweats, trauma, neurologic or GI symptoms. On exam he was a healthy appearing male with previously unnoticed 2 crusted, raised lesions measuring 2.5 Â 2.5 cm on the left arm. These lesions had not been documented during his earlier visit notes though patient admitted to having these lesions for many months. He also had 3 left foot lesions, 1 on the heel and 2 draining lesions on the left malleolus. A plain film of left ankle revealed a lytic area in the distal tibial metaphysis. Bone scan was consistent with acute osteomyelitis. Biopsy of left bony lesion revealed chronic inflammation & giant cells but negative AFB stains and routine cultures. On H & E stain, a multinucleated, thick double contoured wall of yeast with single, broad-based buds was visualized consistent with BD. The patient had complete resolution of all skin lesions and CXR after 6 months of itraconazole treatment. IMPLICATIONS/DISCUSSION: BD is a fungus found in the soil and causes multisystemic pyogranulomatous disease. Blastomyces in endemic in areas bordering Mississippi and Ohio river basins and the Great Lakes. Initial infection is usually via the lungs, can be asymptomatic in 50% of patients or be mistaken for the flu or pneumonia. Pulmonary manifestations include involvement of upper lobes with cavitation, mass lesion with productive cough, hemoptysis, dyspnea, pleuritic chest pain, low grade fever, night sweats, and weight loss. Skin lesions are usually painless, nonpruritic, hyperkeratotic, ulcerative plaques on the face or extremities and may involve mucosa of nose, mouth and larynx. Other common sites of involvement include bone, genitourinary tract or CNS. If untreated, the clinical course can be months to years with remissions, exacerbations and progression in size. The rapid method of diagnosis is visualization of budding yeast in KOH mounts of pus from lesions. Definitive diagnosis is by growth of organism in culture. Treatment consists of 6 months of itraconazole in immunocompetent patients. Amphotericin B is used in patients who are pregnant, seriously ill & immunocompromised, with CNS infection or progressive disease on itraconazole. Our case stresses the importance of a thorough history and physical for appropriate management especially in a disease that is known as the great masquerader.