Background <p>Sarcoidosis is a multisystem granulomatous disorder that predominantly affects the lungs, though extrapulmonary involvement significantly increases morbidity. To our knowledge, reports of simultaneous pulmonary, cardiac, and bone marrow sarcoidosis are exceedingly rare. This report describes a unique case of tri-organ disseminated sarcoidosis in an elderly patient, highlighting the ‘diagnostic ceiling’ that often complicates the recognition of systemic disease in older populations.</p> Case Presentation <p>A 73-year-old female with known Stage I pulmonary sarcoidosis presented with hypoxic respiratory failure and pancytopenia. Diagnostic imaging revealed progressive pulmonary infiltrates and, via cardiac PET (SUV 6.7), occult cardiac involvement—a modality necessitated by MRI-incompatible hardware. Histological confirmation of disseminated disease was obtained through bone marrow biopsy, which showed non-caseating granulomas. This rare tri-organ manifestation was treated with dual-therapy prednisone and infliximab, resulting in clinical stabilization and a transition to a six-month steroid taper.</p> Discussion <p>Simultaneous tri-organ sarcoidosis is exceedingly rare and carries a high mortality risk due to cardiac and hematologic complications. This case demonstrates that when traditional imaging is contraindicated, multimodality assessment with PET and bone marrow biopsy is essential for identifying disseminated disease. Given the severity of cardiac and marrow involvement, early initiation of infliximab alongside corticosteroids may be superior to traditional steroid-sparing agents. Clinicians must maintain a high index of suspicion for systemic sarcoidosis in older patients presenting with new-onset cytopenias or cardiac symptoms.</p>