Chapter 054. Skin Manifestations of Internal Disease (Part 27) a Also associated with systemic diseases. b Reviewed in section on Purpura. cReviewed in section on Papulonodular Skin Lesions. d Favors plantar surface of the foot. Note: TEN, toxic epidermal necrolysis. Livedoid vasculopathy (livedoid vasculitis; atrophie blanche) represents a combination of a vasculopathy plus intravascular thrombosis. Purpuric lesions and livedo reticularis are found in association with painful ulcerations of the lower extremities. These ulcers are often slow to heal, but when they do, irregularly shaped white scars are formed. The majority of cases are secondary to venous hypertension, but possible underlying illnesses include cryofibrinogenemia and disorders of hypercoagulability, e.g., the antiphospholipid syndrome (Chaps. 111 and 313). In pyoderma gangrenosum, the border of the ulcers has a characteristic appearance of an undermined necrotic violaceous edge and a peripheral erythematous halo. The ulcers often begin as pustules that then expand rather rapidly to a size as large as 20 cm. Although these lesions are most commonly found on the lower extremities, they can arise anywhere on the surface of the body, including sites of trauma (pathergy). An estimated 30–50% of cases are idiopathic, and the most common associated disorders are ulcerative colitis and Crohn's disease. Less commonly, pyoderma gangrenosum is associated with seropositive rheumatoid arthritis, acute and chronic myelogenous leukemia, hairy cell leukemia, and myelofibrosis. Additional findings in these patients, even those with idiopathic disease, are cutaneous anergy and a monoclonal gammopathy, usually IgA. Because the histology of pyoderma gangrenosum may be nonspecific (dermal infiltrate of neutrophils when in untreated state), the diagnosis is usually made clinically and includes excluding less common causes of similar-appearing ulcers such as necrotizing vasculitis, Meleney's ulcer (synergistic infection at a site of trauma or surgery), dimorphic fungi, cutaneous amebiasis, spider bites, and factitial. In the myeloproliferative disorders, the ulcers may be more superficial with a pustulobullous border, and these lesions provide a connection between classic pyoderma gangrenosum and acute febrile neutrophilic dermatosis (Sweet's syndrome). Fever and Rash The major considerations in a patient with a fever and a rash are inflammatory diseases versus infectious diseases. In the hospital setting, the most common scenario is a patient who has a drug rash plus a fever secondary to an underlying infection. However, it should be emphasized that a drug reaction can lead to both a cutaneous eruption and a fever ("drug fever"), especially in the setting of DRESS. Additional inflammatory diseases that are often associated with a fever include pustular psoriasis, erythroderma, and Sweet's syndrome. Lyme disease, secondary syphilis, and viral and bacterial exanthems (see "Exanthems," above) are examples of infectious diseases that produce a rash and a fever. Lastly, it is important to determine whether or not the cutaneous lesions represent septic emboli (see "Purpura," above). Such lesions usually have evidence of ischemia in the form of purpura, necrosis, or impending necrosis (gunmetal-gray color). In the patient with thrombocytopenia, however, purpura can be seen in inflammatory reactions such as morbilliform drug eruptions and infectious lesions. Further Readings Bolognia JL et al: Dermatology, 2d ed. Philadelphia, Mosby, 2007 Braverman IM: Skin Signs of Systemic Disease , 3d ed. Philadelphia, Saunders, 1998 Callen JP et al: Dermatological Signs of Internal Disease , 3d ed. Philadelphia, Saunders, 2003 McKee PH et al: Pathology of the Skin, 3d ed. London, Elsevier, 2005 Spitz JL: Genodermatoses: A Clinical Guide to Genetic Skin Disorders , 2d ed. Lippincott Williams & Wilkins, 2004 . Chapter 054. Skin Manifestations of Internal Disease (Part 27) a Also associated with systemic diseases. b Reviewed in section on Purpura. cReviewed in section on Papulonodular Skin. Philadelphia, Mosby, 2007 Braverman IM: Skin Signs of Systemic Disease , 3d ed. Philadelphia, Saunders, 1998 Callen JP et al: Dermatological Signs of Internal Disease , 3d ed. Philadelphia, Saunders,. in the setting of DRESS. Additional inflammatory diseases that are often associated with a fever include pustular psoriasis, erythroderma, and Sweet's syndrome. Lyme disease, secondary