A 42-year-old man with a history of intravenous drug use presents to the emergency department with fever, malaise, and a new cardiac murmur. On examination, you notice flat, non-tender erythematous lesions on his palms and soles. The structure marked **B** in the diagram represents the characteristic appearance of these lesions. Which of the following best describes the pathophysiological basis of the lesions marked **B**?

Explanation

## Why "Septic emboli from infected heart valve vegetation lodging in dermal capillaries" is right Janeway lesions, marked as **B** in the diagram, are non-tender, macular (flat) erythematous lesions on the palms and soles that represent septic emboli from infected valvular vegetations in infective endocarditis. These emboli lodge in dermal capillaries, causing the characteristic flat, painless appearance. This distinguishes them from other vascular phenomena in IE and is a minor Duke criterion for diagnosis (Robbins 10e Ch 12; Harrison 21e Ch 128). ## Why each distractor is wrong - **Immune complex deposition in the dermis causing vasculitis and nodule formation**: This describes Osler nodes, not Janeway lesions. Osler nodes are tender, raised nodules on fingertips and toe pads caused by immune complex deposition, not septic emboli. - **Retinal hemorrhages with white centers due to septic emboli in the retinal vasculature**: This describes Roth spots, a fundus finding in IE, not a cutaneous lesion. While both are minor Duke criteria, Roth spots are found on ophthalmoscopy, not on palms/soles. - **Tender, raised nodules on fingertips and toe pads resulting from immune complex deposition**: Again, this is the definition of Osler nodes. The key distinguishing feature of Janeway lesions is that they are non-tender and macular (flat), not raised and tender. **High-Yield:** Janeway = flat, non-tender, septic emboli (palms/soles); Osler = raised, tender, immune complex (fingertips/toe pads); Roth = retinal hemorrhages with white centers. [cite: Robbins 10e Ch 12; Harrison 21e Ch 128]