Home Renovation Gone Wrong: A Curious Case of Disseminated Blastomycosis

A 46-year-old woman with a history of migraines presented with progressive left knee pain following routine exercise. Initial MRI demonstrated findings consistent with a ligamentous sprain, popliteus strain, proximal tibial marrow edema, and joint effusion, raising concern for a stress fracture and leading to conservative management. Over subsequent days, she developed worsening fatigue, malaise, exertional dyspnea, and hypoxia. Chest CT revealed bilateral ground-glass opacities without pulmonary embolism, and she was treated empirically for community-acquired pneumonia. An acute mid-soleal vein thrombosis was also identified, prompting initiation of anticoagulation. Despite therapy, her systemic symptoms progressed, with rising inflammatory markers. Follow-up MRI of the tibia revealed a new 9 mm lytic lesion with cortical breakthrough and periosteal reaction, concerning for malignancy. Extensive hematologic evaluation, including serum and urine immunofixation and skeletal survey, was unrevealing. Given persistent symptoms, recent travel, and exposure to building renovation, an infectious etiology was pursued. Broad testing was notable only for a positive Blastomyces urine antigen. Shortly thereafter, she developed characteristic cutaneous lesions, confirming disseminated blastomycosis with pulmonary, osseous, and cutaneous involvement. Treatment with intravenous amphotericin B resulted in clinical improvement. This case underscores the diagnostic challenges of osseous blastomycosis, which can mimic malignancy or bacterial osteomyelitis, and highlights the importance of maintaining a high index of suspicion for fungal infection in patients with unexplained bone lesions and systemic symptoms.