Pathophysiology
1) largely a disease of children 2) causes include infection with enterohemorrhagic E. coli (serotype 0157:H7) or Shigella dysenteriae 3) closely resembles thrombotic thrombocytopenic purpura (which is not linked to infections)
Signs and Symptoms
1) hemorrhagic diarrhea 2) rapidly progressive renal failure with oliguria and anuria 3) fever 4) hypertension 5) dyspnea 6) weakness 7) purpura 8) pulmonary edema 9) CNS sequelae – encephalopathy, seizures, and posturing 10) results in death in 10% of cases, even with aggressive treatment
Associated Conditions
increased incidence with 1) 4-8 weeks use of chemotherapy durgs (cisplatin, bleomycin, and especially mitomycin 2) bone marrow transplantation 3) shigellosis
Biochemistry
increased erythropoiesis (not decreased as expected)
Inheritance/Epidemiology
onset can sometimes be related to ingesting foods contaminated wtih the offending organisms (poorly cooked hamburger)
Treatment
1) plasmapheresis/plasma exchange 2) reverses hematologic derangement but does not reverse renal failure
Tips for USMLE
1) does not cause significant vascular disease outside of kidney 2) there is no DIC; thus if question mentions DIC, it is not HUS 3) if a 6 year-old eats rare hamburger and then 6 days later has a fever, a purpura rash, starts to retain fluid, and stops urinating, think HUS 4) if oliguria and anemia occurs two months after mitomycin treatment, think HUS
Characteristic Test Findings
Laboratory – 1) thrombocytopenia (low platelets) 2) microangiopathic hemolytic anemia 3) reticulocytosis 4) increased serum LDH 5) increased serum creatinine 6) presence of Shiga-like toxin 7) hemoglobinurina (hemoglobin in urine) 8) hyponatremia (low blood sodium) 9) hypoglycemia (low blood sugar)
Histology/Gross Pathology
1) platelet aggregates in renal microvasculature 2) thrombotic microangiopathy in kidney 3) moderate endothelial cell proliferation 4) focal areas of endothelial cell swelling 5) focal loss of epithelial cell foot precesses on electron microscopy 6) deposition of fibrin in walls of capillaries and arterioles 7) “flea-bitten” kidneys
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