Scenario F/ 86 Autoimmune hypothyroidism since 2001 Spontaneous bruising for 2 wks: neck, upper limbs, thigh, flank Increasing neck swelling with respiratory arrest on day 1, intubated and transferred to ICU

Scenario APTT level – 77 second PT, platelet level – normal Hb 6.6 (prev Hb 12.4) Mixing test APTT 85.7 s APTT (1:1) mix 49.3 s APTT (1:1) mix 37C 1 hr 72.5 s

Cause of bleeding tendency? Ddx: Specimen contaminated by heparin Lupus anticoagulant Acquired inhibitors of the intrinsic factor pathway (VIII, IX, XI, XII) Acquired von Willebrand disease

Scenario Factor VIII inhibitor level: 40 Bethesda Unit Factor VIII level: 5 U/dL (Normal: 50-200) Dx: Acquired hemophilia A due to inhibitor to factor VIII

Scenario Given recombinant factor VIIa (Novo-seven) 4800mcg (90mcg/kg) iv bolus for total 8 dose during first 1 week of admission

Prednisolone 40mg/d + MMF 1g bd since 12/6/07 Factor VIII inhibitor level 40 BU 14 BU

Diagnostic tests – Mixing test Identify whether inhibitor is present, but not inhibitor’s specificity Step 1: Establish whether a circulating anticoagulant / inhibitor is present Mix equal amounts of the patient’s plasma (containing and normal plasma Measure APTT Immediately After incubation at 37 degrees for 1 to 2 hrs

Diagnostic tests – Mixing test Immediate result Correction of the prolonged APTT  factor or vWF deficiency Persistent prolongation of APTT  inhibitor is present Post-incubation result Some inhibitor has delayed reactivity: APTT corrected immediately after mixing, but prolong again after incubation

Diagnostic tests – Mixing test Step 2: Differentiate whether the circulating anticoagulant is an autoAb directed against a clotting factor / against cell membrane phospholipids Add a source of phospholipid to the mixed plasma Correction of APTT  autoAb against phospholipid Persistent prolongation of APTT  autoAb against a clotting factor  perform the Bethesda assay

Diagnostic tests – Bethesda assay Use: Quantifies the antibody titre Method: Incubate serial dilutions of patient’s plasma with normal plasma at 37 degrees for 2 hrs Measure the residual FVIII activity Definition: Number of dilution of patient’s plasma that result in 50% decrease in factor VIII activity Higher BU  more inhibitor

Acquired Haemophilia

Acquired vs Congenital No genetic inheritance pattern M = F Median age of presentation: 60 – 70 yrs Bleeding pattern Congenital – haemathroses Acquired – soft tissue bleeding, muscle bleeding, haematuria, GI bleed May present with persistent bleeding after a surgical procedure Increased mortality

Acquired hemophilia Most common is against factor VIII Others: factor v, vii, ix, x, xi, xiii

Factor VIIIa as a cofactor to IXa Forms a complex with factor X, IXa, phospholipid surface Increase the catalytic efficiency of factor IXa toward factor X (X  Xa) Blood Reviews 2004; 18:1-15

Anti FVIII Ab prevents F VIII from interaction with its 4 partners – phospholipid surface (PLs), vWF, factors IX, X Thromb Haemost 2005; 94:760-9

172 patients identified in 2 yrs Incidence: 1.48 per million per yr Median age 78 yrs Male 43% Female 57 %

Presenting characteristics – Age % with underlying diagnosis < 40 yrs – 100% 40-59 yrs – 55% 60-79 yrs – 42% > 80 yrs – 23%

Disease associations No (%)

Presenting characteristics – Levels of FVIII

Presenting characteristics – Bleeding 34% patients do not require haemostatic treatment 2 patients were asymptomatic

Fatal bleeding Bleeding is the cause of death in 9.1% at a median of 19 days Fatal bleeding can occur up to 5 mths after presentation if the inhibitor is not eradicated. Factor VIII and inhibitor titre at presentation were not useful for predicting the severity of bleeding events. Median inhibitor level was similar for those with fatal bleed and those who require no haemostatic therapy

Management options

Goal of Treatment Control bleeding Eradication of the inhibitor Agents that increase F VIII levels DDAVP Factor VIII concentrates F VIII bypassing agents Activated prothrombin complex concentrates Recombinant factor VIIa Eradication of the inhibitor Immunosuppression Biological therapy

Increase F VIII levels DDAVP Factor VIII concentrates Release endogenous FVIII protein Transient rise in factor VIII For patients with very low inhibitor titres <3 BU Factor VIII concentrates Transient - High Ab titres rapidly inactivate FVIII concentrates For patients with low inhibitor titres <5 BU FFP and cryoprecipitate do not contain sufficient FVIII to overcome the inhibitor  rarely effective

F VIII bypassing agents - aPCC For patients with severe bleeding or inhibitor titre > 5 BU Each vial contains Factor IX, X, II F IXa generate additional F VIIa Antithrombin III Inactivates F Xa and thrombin Heparin Minimal amount, to forestall risks of thrombosis and DIC Low levels of factors V and VII aPCC 75 units/kg every 8-12 hrs Max dose of 200 units/kg within a 24 hr period Risk of thromboembolism, MI, DIC

Recombinant factor VIIa Brand-name: Novo-Seven Mechanism Form a complex with tissue factor  local thrombin generation Activate F X (independent of tissue factor) on the surface of activated platelets Dose 90 – 120 microgram/kg every 3 hrs Short t ½ 2.7 hrs Bolus dose, given over 2-5 min

Recombinant factor VIIa At high dose, rFVIIa binds activated platelet independent of TF Localization activity -> relative lack of thrombotic complication

rFVIIa 74 bleeding episodes in 38 patients with acquired haemophilia Median dose 90 microgram/kg every 2-6 hrs Median no of doses: 28 per episode Median duration of treatment 3.9 days Response As initial therapy: 100% response rate Salvage therapy: 75% good response rate 17% partial response 8% poor control of bleeding Those patients who did not respond within 24 hrs were unlikely to respond if rVIIa was continued. Thromb Haemost 1997; 78:1468-7 Define response

aPCC vs rVIIa No direct comparison studies APCC rVIIa Adv of dosing every 8-12 hrs Cost $0.8/units. i.e. 70 units/kg q8hr = $ 2,800 q8hr Thrombosis risk rVIIa Recombinent protein, less likely to be contaminated with infectious agents Infused every 2-3 hrs More costly $ 4,742.50 per vial (1.2 mg) -- $20,000 for each injection

Inhibitor elimination Prednisolone 1 mg/kg/day Inhibitor abolition in approx 30% of patients + Cyclophosphamide 1 to 2 mg/kg Increase response rate to 60-70% Slow response in 3-6 wks, some may have a prolonged response time of mths Relapse is not uncommon Cyclosporin Use alone or with prednisolone Esp effective in patients with underlying SLE

Outcome – UK study Outcome between different treatment gps 144/151 (95%) were treated with immunosuppression Steroid alone – 40 patients (26%) Concomitant steroids and cytotoxics – 48 patients (31%) The patient gp treated with steroids alone had a lower median inhibitor titre (p <0.01) and factor VIII level (not sig) But neither the inhibitor titre and factor VIII level were associated with outcome

Outcome – Inhibitor eradication Complete remission – defined as Normal factor VIII level, undetectable inhibitor level Immunosuppression stopped or reduced to doses used before acquired haemophilia develop Without relapse

Outcome – Inhibitor eradication 102/144 patients (71%) achieve CR Mean time to remission All patients – 57 days Steroids alone – 49 days Steroids + cytotoxics – 39 days (P = 0.51) No difference between steroid gp and steroid + cytotoxic gp (irrespective of treatment order)

Outcome – Inhibitor relapse 18 / 90 patients (20%) had a relapse Median time to relapse 7.5 mths after stopping immunosuppression (range 1 to 14 mths) Out of the 18 patients 10 patients (56%) achieve a second CR 4 patients (22%) has inhibitor eradicated and factor VIII normalized, but immunosuppression could not be stopped without a relapse 4 patients (22%) could not achieve a second remission

Outcome – Survival No difference between steroid gp and steroid + cytotoxic gp (irrespective of treatment order) Median survival time between presentation and death Steroid alone – 767 days Steroids + cytotoxics – 975 days

Outcome -ve predictors of outcome Not predictors Age Underlying diagnosis (except for postpartum) Factor VIII level, inhibitor titre at diagnosis

Conclusions Acquired Hemophilia A May not have bleeding, but fatal bleeding remains a risk if inhibitor not eradicated. No clinical or laboratory features identify the high-risk patients All patients advised immuno-suppressed once diagnosed Tx with steroid or steroid + cytotoxics

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