Skin lesions that can be useful in the diagnosis of acute or chronic polyarthritis
• Erythema chronicum migrans (Lyme arthritis)
• Erythema nodosum (sarcoid arthritis, enteric arthritis)
• Psoriatic plaques (psoriatic arthritis)
• Keratoderma blennorrhagicum (reactive arthritis)
• Erythema marginatum (acute rheumatic fever)
• Palpable purpura (vasculitis)
• Livedo reticularis (vasculitis, antiphospholipid antibody syndrome)
• Vesiculopustular lesions or hemorrhagic papules (gonococcal arthritis)
• Butterfly rash, discoid lupus, or photosensitive rash (SLE)
• Thickening of the skin, digital pitting/ulcers, telangiectasias (systemic sclerosis)
• Heliotrope rash on eyelids, upper chest, and extensor aspects of joints (dermatomyositis)
• Gottron’s papules overlying the extensor aspects of the metacarpophalangeal and interphalangeal joints of the hands (dermatomyositis)
• Gray/brown skin hyperpigmentation (hemochromatosis)
• Periungual nodules (multicentric reticulohistiocytosis)