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Hemolytic Uremic Syndrome Beatrice Goilav, M.D. Pediatric Nephrology Children’s Hospital at Montefiore Albert Einstein College of Medicine Disclosures Nothing to disclose. Outline Background/Epidemiology and other things to know on “classical” diarrheaassociated HUS The “funky” types of HUS Atypical, non-diarrhea associated, recurrent, familial What you should know about atypical HUS and what to do with that information THE HISTORY OF HUS Gasser C, et al. 1955 First description Self-limited illness associated with a prodrome of diarrhea that results in Einstein’s first job was here spontaneous recovery I was born here Conrad Gasser (1912-1982) DIAGNOSTIC COMPONENTS AND HISTOPATHOLOGY Hemolytic Uremic Syndrome (HUS) Triad Microangiopathic hemolytic anemia Thrombocytopenia Acute kidney injury Thrombotic Microangiopathy (TMA) Hemolytic Uremic Syndrome Thrombotic Thrombocytopenic Purpura Hemolytic Anemia Microangiopathic hemolytic anemia with erythrocyte fragmentation Coombs negative Plasma LDH elevated Haptoglobin decreased Most sensitive marker to track resolution of intravascular hemolysis Severity does not correlate with clinical outcome Red cell production increased Thrombocytopenia Variable and transient May be missed Consumption of platelets Majority of platelets removed in reticuloendothelial system Significant bleeding rare! Slightly pro-thrombotic state Acute Kidney Injury Abrupt Oligoanuria Proteinuria Hypertension Severe and difficult to control in atypical forms Absent or mild in infection-associated form – delayed to recovery period Thrombotic Microangiopathy (TMA) Histopathological term Characterized by presence of Platelet-fibrin thrombi within the vascular lumen Injury to endothelial cells with separation from underlying basement membrane Deposition of eosinophilic material Risk Factors for Development of HUS Female gender Severe colitis Fever Leukocytosis Also: Younger age Antimotility agents Antibiotics Alterations in gene for factor H Implicated in pathophysiology of atypical HUS Some Statistical Data Most common cause of acute kidney injury in childhood Incidence: 3-5/100,000 population in children age 118 Gradual decline from early childhood to adolescence Significant morbidity and mortality in acute phase Mortality: 3-5%, usually associated with severe extra-renal disease Primary diagnosis for up to 4.5% of children on chronic renal replacement therapy M&M Mortality 3-5% Serious extra-renal complications 20% Need for acute dialysis 40% Persistent renal injury 20%; hypertension, proteinuria, reduced GFR Terminology/Categories Term Comment D+ HUS Patient presents with prodrome of diarrhea in past 2 weeks Typical HUS D+ HUS, diagnosis made in retrospect; single, selflimited event Atypical HUS Any pattern of clinical presentation other than D+ HUS – implies complement dysregulation Recurrent or relapsing HUS Repeat episode of same clinical features, implies repeat injury to kidneys – strongly suggests genetic or autoimmune risk factor Thrombotic microangiopathy, glomerular thrombotic microangiopathy Pathological descriptive terms Familial HUS Unclear term. Not distinguishing between Synchronous HUS = several family members infected with EHEC at the same time; and Asynchronous HUS = implies inherited risk factor D+ HUS Diagnosis Clinical - Abrupt onset of illness Recognized within 24 hours of onset Lethargy Pallor Oliguria Laboratory abnormalities: Coombs-negative anemia and thrombocytopenia Rising BUN/Creatinine Elevated LDH Low haptoglobin Clinical Time Course Ingestion of bacteria Enterocolitis within 2-3 days Bloody stools in >85% Fever Severe abdominal pain Most cases: self-limited, complete resolution 5-10% progress to HUS Monophasic illness Route of Infection Most Common Etiology Worldwide Enterohemorrhagic E. coli (EHEC) O157:H7 D+ HUS (typical) Produces Shiga toxin (Stx) 1 and/or 2 Encoded on a phage Other E. coli strains also produce Stx Called Stx-producing E. coli (STEC) Over 400 seropathotypes Pathogenesis Shiga toxin (Stx)-induced injury to endothelial cells Activation of prothrombotic coagulation cascade Release of inflammatory mediators and chemokines Molecular Risk Assessment Association of virulence genes with severity of disease Presence or absence of genes (binary typing) produces genetic fingerprint for each isolate Identify strains that have greater potential to cause harm = molecular risk assessment Binary Typing of Virulence Genes Distribution of 41 virulence genes in STEC isolates “Virulence bar code” for each isolate Integrated epidemiological data Allows some prediction of clinical course Brandt SM et al. Appl Environ Microbiol. 2011 Apr;77(7):2458-70. Brandt SM et al. Appl Environ Microbiol. 2011 Apr;77(7):2458-70. Virulence Factors Seropathotype (SPT) classification identifies STEC serotypes linked to outbreaks and/or serious disease SPT A (O157:H7, O157:NM) and SPT B (O26:H11/NM, O103:H2, O111:H8/NM, O121:H19, O145:NM) associated with outbreaks and HUS SPT C (e.g., O5:NM, O91:H21, O113:H21, O121:NM, O128:H2) associated with sporadic cases of HUS but not with outbreaks SPT D includes remainder of STEC serotypes that have been reported to cause sporadic disease and association with diarrhea but not HUS SPT E not associated with human illness Therapy Nothing proven Intensive, supportive medical care Dialysis if: Anuria x 24 h Oliguria (urine output <0.5ml/kg/h) x 48-72 h pRBC Transfusion if: Hemoglobin <6 g/dl Ineffective treatments are: Antiplatelet drugs, fibrinolytic agents, IVIG, high-dose steroids, plasmapheresis, and oral Stx-binding agents Careful Monitoring Electrolyte abnormalities Hyponatremia Hypocalcemia LDH, serum creatinine, Hgb, platelets Watch out for : Seizures Pancreatitis Myocardial dysfunction Adult respiratory distress syndrome Sudden neurologic deterioration Prevention of HUS – The Scientific Approach Subcutaneous mouse vaccine against stx and intestinal zonula occludens toxins Decreased shedding of E. coli O157:H7 Good news: mice TOLERATED vaccine WELL Bad news: MICE tolerated vaccine well Prevention of HUS – The Useful Approach Changes in feed provided to cattle Tighter regulation of meat processing plants Irradiation of food and beverages No antibiotics in children with bloody diarrhea Prompt hospitalization and administration of isotonic parenteral fluids Prevent vascular injury in glomerular microcirculation Isolate sick individual from other family members D- HUS Atypical, Sporadic, Non-Familial HUS Pneumococcus-related disease Younger children Number of cases requiring dialysis is higher Worse prognosis compared with STEC-related HUS Other causes: HIV infection, use of calcineurin inhibitors, OCP, SLE (usually in presence of antiphospholipid syndrome), and HELLP syndrome Atypical HUS Atypical HUS Annual incidence of genetic forms of aHUS: 10% of D+HUS 3-5 cases per 1 million Strong association between aHUS and mutations and/or polymorphisms in complement gene (regulatory and activation proteins) 50% of cases linked to genetic mutations in alternate cascade Modulators of Alternate Complement Cascade Loss-of-function mutations in regulatory proteins or gain-of-function mutations in factor B and complement 3 Three most common defects: Mutation in factor H: 25-35% not to be confused with Mutation in factor I: 5-10% Mutation in membrane co-factor protein (MCP = CD46): 3-5% Deficiency in factor H-related proteins (CFHR15) Polymorphic delCFHR1/3 deletion strongly associated with CFH autoantibodies aHUS due to CFH auto-antibodies more common in children Clinical Course of aHUS Onset of syndrome frequently preceded by environmental insult (e.g., infection) Typically infants/young children C3 level may be normal CFH mutations predominantly result in impaired ability of CFH to interact with cell surfaces, but ability to regulate plasma C3 preserved Clinical Relevance of Genetic Testing Important to test for CFH auto-antibodies strategies to reduce auto-antibody titer (e.g. plasma exchange) Higher relapse rate Increased likelihood of progression to end-stage kidney disease High rate of recurrence after kidney transplant Factor H or I mutation >> MCP mutation MCP present in transplanted kidney – prevents complement-mediated injury to allograft Therapy of Genetic aHUS Plasma Intermittent infusions or via plasmapheresis Treatment intensity guided by disease activity: Platelet count LDH level Serum creatinine concentration If suspecting genetic form of aHUS, initiate daily plasma therapy promptly Combined kidney/liver transplant For cases with factor H and factor I mutations Hepatic production of normal complement regulators Plasma Therapy Not THIS one! Plasma Therapy Complement 5 Protein Critical role in development of aHUS CFH-deficient animals expressing mutant CFHD16–20 protein develop spontaneous aHUS C5 knockout in this model results in resistance to aHUS. Eculizumab Recombinant, humanized, monoclonal Ab produced from mouse myeloma cells Approved for treatment of paroxysmal nocturnal hemoglobinuria (PNH) Reduces intravascular hemolysis, anemia, thrombotic events, and transfusion requirements in PNH Targets complement protein C5 and prevents generation of proinflammatory peptide C5a and cytotoxic membrane attack complex C5b-9 Regimen Weekly infusions with gradual increase in dosing with biweekly maintenance therapy Shown to completely block complement activity Complement blockade confirmed by CH50 measurements Dosing and pharmacokinetics in children are underway in international multi-center study – Children’s Hospital at Montefiore to be added as site within next 2 months Thrombotic Thrombocytopenic Purpura TTP – Moschcowitz Syndrome An acute febrile pleiochromic anemia with hyaline thrombosis of terminal arterioles and capillaries: An undescribed disease. Archives of Internal Medicine, Chicago, 1925, 36: 89. Deficiency of von Willebrand Protease (ADAMTS13) = a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 Thrombocytopenia Microangiopathic hemolytic anemia Neurological symptoms Renal dysfunction Fever Role of ADAMTS13 (or a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) ADAMTS13 Deficiency (you know what is supposed to be written here) Cause: Rare: loss-of-function mutation (Congenital TTP) Acquired inhibitor: IgG auto-antibody Associated with use of Clopidogrel and Ticlopidine Effect: Ultra-large vWF multimers ADAMTS13 (guess what?) Deficiency Enzyme activity of <5% is primary cause of microvascular thrombosis Enzyme activity <30% in several disease and physiological states Thrombi found at arteriolar-capillary junction – area of high shear stress Affected organs: Brain, heart, spleen, kidney, pancreas, adrenals, lungs, and eyes Outcome of TTP Mortality: Historically: 95% Today: 20% What made the difference? Plasma therapy The Weird Ones HUS can be also caused by: Cobalamin deficiency Quinine/Quinidine Defect in methylmalonic aciduria and homocystinuria gene (MMACHC) Found in tonic water and tablets that prevent muscle cramps Autoantibodies to ? Really rare ones: Use of anti-VEGF monoclonal antibodies Disseminated adenocarcinoma Questions? Not related to me, no idea who he is, but love his hair