Skin Signs of Systemic Disease

Key points

• Acanthosis nigricans: velvety hyperpigmented flexures — insulin resistance, internal malignancy (gastric).
• Pyoderma gangrenosum: painful ulcer with undermined violaceous edge — IBD, rheumatoid arthritis, haematological malignancy; pathergy (worsens with debridement).
• Necrobiosis lipoidica: shiny atrophic yellow-brown plaques on shins — diabetes.
• Granuloma annulare: annular dermal papules (hands/feet) — diabetes association in generalised form.
• Dermatomyositis: heliotrope rash (violaceous eyelids) + Gottron's papules (over knuckles) + proximal myopathy — malignancy screen in adults.