A 32-year-old African-American woman presents with a 6-week history of dry cough, exertional dyspnea, and fatigue. She has tender erythematous nodules on both shins, arthralgias affecting the ankles, and anterior uveitis on slit-lamp examination. Chest radiograph shows the classic "1-2-3 sign" with right paratracheal lymphadenopathy and symmetric bilateral hilar lymphadenopathy. The structure marked **C** (left hilar lymphadenopathy) is part of the radiographic hallmark that defines which Scadding stage of pulmonary sarcoidosis?

Why Stage I is right

The radiographic hallmark that defines Scadding Stage I pulmonary sarcoidosis is symmetric bilateral hilar lymphadenopathy without parenchymal involvement. The structure marked C (left hilar lymphadenopathy), together with right hilar lymphadenopathy (B) and right paratracheal lymphadenopathy (A), forms the classic "1-2-3 sign" or Garland triad. The presence of clear lung fields (D) confirms the absence of parenchymal disease, placing this patient in Stage I. This constellation of findings—bilateral hilar lymphadenopathy with clear lungs—is the defining radiographic criterion for Stage I, regardless of extrapulmonary manifestations such as erythema nodosum or uveitis (Lofgren syndrome).

Why each distractor is wrong

Harrison's Principles of Internal Medicine, 21st Edition, Chapter 360: Sarcoidosis