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....
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Chapter 054. Skin Manifestations of Internal Disease (Part 24) Chapter 054. Skin Manifestations of Internal Disease (Part 24) Systemic causes of nonpalpable purpura fall into several categories, andthose secondary to clotting disturbances and vascular fragility will be discussedfirst. The former group includes thrombocytopenia (Chap. 109), abnormal plateletfunction as is seen in uremia, and clotting factor defects. The initial site ofpresentation for thrombocytopenia-induced petechiae is the distal lower extremity.Capillary fragility leads to nonpalpable purpura in patients with systemicamyloidosis (see Papulonodular Skin Lesions, above), disorders of collagenproduction such as Ehlers-Danlos syndrome, and scurvy. In scurvy there areflattened corkscrew hairs with surrounding hemorrhage on the lower extremities,in addition to gingivitis. Vitamin C is a cofactor for lysyl hydroxylase, an enzymeinvolved in the posttranslational modification of procollagen that is necessary forcross-link formation. In contrast to the previous group of disorders, the purpura seen in thefollowing group of diseases are associated with thrombi formation within vessels.It is important to note that these thrombi are demonstrable in skin biopsyspecimens. This group of disorders includes disseminated intravascular coagulation(DIC), monoclonal cryoglobulinemia, thrombotic thrombocytopenic purpura, andreactions to warfarin and heparin (heparin-induced thrombocytopenia andthrombosis). DIC is triggered by several types of infection (gram-negative, gram-positive, 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 associatedwith fever and hypotension that occurs more commonly in children following aninfectious illness such as varicella, scarlet fever, or an upper respiratory tractinfection. In both disorders, hemorrhagic bullae can develop in involved skin. Monoclonal cryoglobulinemia is associated with multiple myeloma,Waldenströms macroglobulinemia, lymphocytic leukemia, and lymphoma.Purpura, primarily of the lower extremities, and hemorrhagic infarcts of thefingers and toes are seen in these patients. Exacerbations of disease activity canfollow cold exposure or an increase in serum viscosity. Biopsy specimens showprecipitates of the cryoglobulin within dermal vessels. Similar deposits have beenfound in the lung, brain, and renal glomeruli. Patients with thromboticthrombocytopenic purpura can also have hemorrhagic infarcts as a result ofintravascular thromboses. Additional signs include thrombocytopenic purpura,fever, and microangiopathic hemolytic anemia (Chap. 101). Administration of warfarin can result in painful areas of erythema thatbecome purpuric and then necrotic with an adherent black eschar; the condition isreferred to as warfarin-induced necrosis. This reaction is seen more often inwomen and in areas with abundant subcutaneous fat—breasts, abdomen, buttocks,thighs, and calves. The erythema and purpura develop between the third and tenthday of therapy, most likely as a result of a transient imbalance in the levels ofanticoagulant and procoagulant vitamin K–dependent factors. Continued therapydoes not exacerbate preexisting lesions, and patients with an inherited or acquireddeficiency of protein C are at increased risk for this particular reaction as well asfor purpura fulminans. Purpura secondary to cholesterol emboli are usually seen on the lowerextremities of patients with atherosclerotic vascular disease. They often followanticoagulant therapy or an invasive vascular procedure such as an arteriogram butalso occur spontaneously from disintegration of atheromatous plaques. Associated findings include livedo reticularis, gangrene, cyanosis, andischemic ulcerations. Multiple step sections of the biopsy specimen may benecessary to demonstrate the cholesterol clefts within the vessels. Petechiae arealso an important sign of fat embolism and occur primarily on the upper body 2–3days after a major injury. By using special fixatives, the emboli can be demonstrated in biopsyspecimens of the petechiae. Emboli of tumor or thrombus are seen in patients withatrial myxomas and marantic endocarditis. In the Gardner-Diamond syndrome (autoerythrocyte sensitivity), femalepatients develop large ecchymoses within areas of painful, warm erythema.Intradermal injections of autologous erythrocytes or phosphatidyl serine derivedfrom the red cell membrane can reproduce the lesions in some patients; however,there are instances where a reaction is seen at an injection site of the forearm butnot in the midbac ...