TAILIEUCHUNG - Chapter 054. Skin Manifestations of Internal Disease (Part 24)

Systemic causes of nonpalpable purpura fall into several categories, and those secondary to clotting disturbances and vascular fragility will be discussed first. The former group includes thrombocytopenia (Chap. 109), abnormal platelet function as is seen in uremia, and clotting factor defects. The initial site of presentation for thrombocytopenia-induced petechiae is the distal lower extremity. Capillary fragility leads to nonpalpable purpura in patients with systemic amyloidosis (see "Papulonodular Skin Lesions," above), disorders of collagen production such as Ehlers-Danlos syndrome, and scurvy. In scurvy there are flattened corkscrew hairs with surrounding hemorrhage on the lower extremities, in addition to gingivitis | Chapter 054. Skin Manifestations of Internal Disease Part 24 Systemic causes of nonpalpable purpura fall into several categories and those secondary to clotting disturbances and vascular fragility will be discussed first. The former group includes thrombocytopenia Chap. 109 abnormal platelet function as is seen in uremia and clotting factor defects. The initial site of presentation for thrombocytopenia-induced petechiae is the distal lower extremity. Capillary fragility leads to nonpalpable purpura in patients with systemic amyloidosis see Papulonodular Skin Lesions above disorders of collagen production such as Ehlers-Danlos syndrome and scurvy. In scurvy there are flattened corkscrew hairs with surrounding hemorrhage on the lower extremities in addition to gingivitis. Vitamin C is a cofactor for lysyl hydroxylase an enzyme involved in the posttranslational modification of procollagen that is necessary for cross-link formation. In contrast to the previous group of disorders the purpura seen in the following group of diseases are associated with thrombi formation within vessels. It is important to note that these thrombi are demonstrable in skin biopsy specimens. This group of disorders includes disseminated intravascular coagulation DIC monoclonal cryoglobulinemia thrombotic thrombocytopenic purpura and reactions to warfarin and heparin heparin-induced thrombocytopenia and thrombosis . DIC is triggered by several types of infection gram-negative grampositive viral and rickettsial as well as by tissue injury and neoplasms. Widespread purpura and hemorrhagic infarcts of the distal extremities are seen. Similar lesions are found in purpura fulminans which is a form of DIC associated with fever and hypotension that occurs more commonly in children following an infectious illness such as varicella scarlet fever or an upper respiratory tract infection. In both disorders hemorrhagic bullae can develop in involved skin. Monoclonal cryoglobulinemia is associated with .