Skin involvement in systemic autoimmune diseases.

Autoimmune diseases present with varied and broad-ranging cutaneous manifestations. Connective tissue disorders have a plethora of skin manifestations such as rheumatoid nodules in rheumatoid arthritis, psoriatic plaques in psoriatic arthritis, acne and pustulosis in SAPHO syndrome, livedo reticularis and ulceration in antiphospholipid antibody syndrome and xerosis in Sjögren syndrome. Cutaneous manifestations of autoimmune vasculitides such as polyarteritis nodosa, Kawasaki disease, Henoch-Schönlein purpura, cryoglobulinemic vasculitis, Behcet disease, Wegener granulomatosis, microscopic polyangiitis and Churg-Strauss syndrome range from papules, subcutaneous nodules and livedo reticularis, to palpable purpura, hemorrhagic bulla and ulcerating lesions. Pathological skin manifestations in autoimmune endocrinopathies include pretibial myxedema/dermopathy in Graves' disease, diabetic dermopathy and necrobiosis lipoidica in type I autoimmune diabetes mellitus, candidiasis, ectodermal dysplasia, vitiligo and alopecia areata in APECED and uniform hyperpigmentation of the skin in Addison's disease. Autoimmune gastrointestinal disorders such as inflammatory bowel disease (with erythema nodosum), gluten-sensitive enteropathy (with dermatitis herpetiformis), autoimmune hepatitis and primary biliary cirrhosis (with jaundice and pruritus), hematologic/oncologic disorders such as acute and chronic graft-versus-host disease (with skin manifestations ranging from pruritic maculopapular eruptions and lichen planus-like lesions to generalized scleroderma), and paraneoplastic autoimmune dermatoses are discussed as well.