tailieunhanh - Chapter 109. Disorders of Platelets and Vessel Wall (Part 8)

Hemolytic Uremic Syndrome HUS is a syndrome characterized by acute renal failure, microangiopathic hemolytic anemia, and thrombocytopenia. It is seen predominantly in children and in most cases is preceded by an episode of diarrhea, often hemorrhagic in nature. Escherichia coli O157:H7 is the most frequent, although not only, etiologic serotype. HUS not associated with diarrhea (termed DHUS) is more heterogeneous in presentation and course. Some children who develop DHUS have been found to have mutations in genes encoding Factor H, a soluble complement regulator, and membrane cofactor protein that is mainly expressed in the kidney. . | Chapter 109. Disorders of Platelets and Vessel Wall Part 8 Hemolytic Uremic Syndrome HUS is a syndrome characterized by acute renal failure microangiopathic hemolytic anemia and thrombocytopenia. It is seen predominantly in children and in most cases is preceded by an episode of diarrhea often hemorrhagic in nature. Escherichia coli O157 H7 is the most frequent although not only etiologic serotype. HUS not associated with diarrhea termed DHUS is more heterogeneous in presentation and course. Some children who develop DHUS have been found to have mutations in genes encoding Factor H a soluble complement regulator and membrane cofactor protein that is mainly expressed in the kidney. Hemolytic Uremic Syndrome Treatment Treatment of HUS is primarily supportive. In D HUS many 40 children require at least some period of support with dialysis however the overall mortality is 5 . In D-HUS the mortality is higher approximately 26 . Plasma infusion or plasma exchange has not been shown to alter the overall course. ADAMTS13 levels are generally reported to be normal in HUS although occasionally they have been reported to be decreased. As ADAMTS13 assays improve they may help in defining a subset that better fits a TTP diagnosis and may respond to plasma exchange. Thrombocytosis Thrombocytosis is almost always due to 1 iron deficiency 2 inflammation cancer or infection reactive thrombocytosis or 3 an underlying myeloproliferative process essential thrombocythemia or polycythemia vera Chap. 103 or rarely the 5q-myelodysplastic process Chap. 102 . Patients presenting with an elevated platelet count should be evaluated for underlying inflammation or malignancy and iron deficiency should be ruled out. Thrombocytosis in response to acute or chronic inflammation has not been associated with an increased thrombotic risk. In fact patients with markedly elevated platelet counts million usually seen in the setting of a myeloproliferative disorder have an increased risk of bleeding.