Thrombotic Microangiopathy in the Transplant Kidney Dr Weng Oh ST7 in renal medicine

Background 33 year old Caucasian female Kidney transplant from brother 2011 Primary renal disease: chronic pyelonephritis Crohns disease Tacrolimus 5mg bd, Azathioprine 100mg od, Prednisolone 5mg od Baseline creatinine: 130 – recent rise to 160 umol/L Urine PCR 49mg/mmol Awaiting transplant biopsy

Admitted 7.8.15 2 week history of RUQ pain Vomiting 8-9x in last 48 hours ‘Not passing as much urine as she ‘s used to’ No recent flare-ups AKI with Creat 330umol/L Denies taking any nephrotoxic agents

8.8.15 Seen by renal on-call team Creat risen further to 471 ABG – no acidosis/hyperkalaemia LFTs and amylase normal Hypovolaemic Urinalysis – 4+blood, 3+ protein USS – normal transplant kidney, no hydronephrosis No evidence of sepsis

Changes in lab parameters

9.8.15 LDH 1644 Platelet 90 – falling Hb 90 Blood film – red cell fragments Plasma exchange started RIJ vascath inserted Methylpred 500mg IV od for 3 days Tacrolimus stopped Azathioprine switched to MMF

Peripheral blood film

10.8.15 Anuric AKI - Commenced on HD Daily plasma exchange against octoplas Transplant biopsy 12.8.15 CT chest/abdo/pelvis – no lymphadenopathy/masses ADAMTS13 test – normal activity On advice of Prof Goodship – commence eculizumab

Histology

Normal Glomerulus

Histology

Histology

Just to recap .. 33 yr old lady Kidney Tx 2011 AKI, TMA Diagnosis: post – transplant TMA

Definition of TMA A pathological process of microvascular thrombosis, consumptive thrombocytopenia and microangiopathic haemolytic anaemia (MAHA) First described by Prof W Symmers in 1952 Hallmarks of TMA Thrombocytopenia MAHA Renal impairment Neurological deficits

TMA – a feature seen in .. HUS Atypical HUS TTP Malignant hypertension Pregnancy Renal transplantation HIV

Post transplant TMA Recurrent disease Drug-induced (Tacrolimus, cyclosporine) Rejection Malignancy

TMA – laboratory features FBC : thrombocytopenia and anaemia Blood film: red cell fragmentation Coombs test: negative Haemolysis screen: elevated bilirubin and LDH, low serum haptoglobins, high reticulocyte count Liver enzymes and coagulation screen: normal Serum creatinine: elevated in renal involvement

TMA – histological features Arteriolar thrombosis Intracapillary glomerular thrombosis Ischaemic glomerular tufts In native kidneys – biopsy adds little diagnostic information In transplant kidneys – biopsy distinguishes antibody –mediated rejection from other causes of TMA

Let’s go back to the patient .. STEC –HUS unlikely as no diarrhoeal prodrome and recurrence is rare in transplants Tacrolimus levels within range Anti HLA antibodies negative No rejection in biopsy Malignant hypertension absent No evidence of malignancy on CT scan Pregnancy test negative TTP less likely given renal involvement and normal activity of ADAMTS13 No family history of renal disease

Is this atypical HUS? Rare genetic condition First reported by Dr Conrad Von Gasser in 1955 Often presents in childhood Diarrhoea prodrome less common Renal involvement predominates Disorder of complement dysregulation a low plasma C3 may be present

Initiation of complement activation, with amplification and downstream effects of the AP. Thomas Barbour et al. Nephrol. Dial. Transplant. 2012;27:2673-2685 © The Author 2012. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved.

Regulation of the AP of complement. Thomas Barbour et al. Nephrol. Dial. Transplant. 2012;27:2673-2685 © The Author 2012. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved.

Pathophysiology of aHUS Disorder of alternative pathway Over-activation of C3 convertase Increased cleavage of C3b C3a and C5a formation Formation of lytic membrane attack complex (MAC) Pathogenic surfaces are not just the target Host cell becomes target – inflammation, cell damage Renal vasculature (glomerular capillaries and arterioles) are site of injury Endothelial cell injury – prothrombotic phenotype

Genetic mutations of aHUS Complement regulatory protein mutation Factor H, Factor I, MCP, Factor B, C3 Autoantibodies (anti CFH) Combined mutations have been reported Mutations carriers have 50% penetrance Genetic/environment modifiers are required for disease penetrance Identification of mutations important as they affect renal survival, transplant outcomes and mortality

Screening tests Complement abnormalities Measure C3, C4, factor H, factor I before onset of plasma exchange Screening for factor H autoantibodies Mutation screening of CFH, CFI, CD46, C3 and CFB Mutation screening of DGKE and THBD (when recommended by national aHUS service)

Treatment Empirical treatment with plasma exchange Methylprednisolone Tacrolimus re-started Azathioprine changed to MMF Eculizumab

Plasma exchange Removes the abnormal complement regulatory proteins and autoantibodies Replace defective complement regulators Started as soon as diagnosis made Should be given daily (minimum 5 days) until LDH, Hb and platelet count normalizes Renal function is a marker Before the introduction of PEX, mortality of TMA was almost 100% PEX has improved survival to 90%

Limitations of plasma exchange Treatment resistant cases Dependence on PEX Requires central vascular access May develop anaphylactic reactions to plasma replacement products

Eculizumab Targets terminal pathway of complement activation Inhibits C5a and formation of C5b-9 (MAC) Prevents MAC attack on endothelial surface However, risk of Nessieria Meningitidis is high – so need vaccination Greater chance of renal recovery with early initiation Recommended once TTP excluded Treat for 6 months minimum Beneficial to those on dialysis as prophylactic treatment to enable renal transplantation

The complement system is a major innate immune defence mechanism. The complement system is a major innate immune defence mechanism. Complement may be activated by the classical, lectin or alternative pathways, all leading to the cleavage of the inactive central component C3 to biologically active C3b. C3b binds covalently to any surface, either foreign or self. When C3b is bound to positively charged surfaces (called alternative pathway activator surfaces as present in microorganisms) C3b interacts with factor B (FB) to form the C3 convertase (C3bBb) of the alternative pathway amplification loop and may generate a C5 convertase leading to the release of C5a, which is also an anaphylatoxin, and C5b which initiates the formation of the membrane attack complex (MAC), by binding C6 and C7. The C5b67 inserts into the membrane where it binds C8 and many molecules of C9, forming a pore. It can be cytolytic, forming a transmembrane channel, which causes osmotic lysis of the target cell or sublytic, associated with cell activation. In order to avoid complement hyperactivation, the alternative pathway C3 convertase is tightly regulated. Veronique Fremeaux-Bacchi Clin Kidney J 2012;5:4-6 © The Author 2012. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com

Nat. Rev. Nephrol. doi:10.1038/nrneph.2012.214 Figure 2 Recovery of renal function is better with a shorter interval between onset of aHUS and initiation of eculizumab Zuber, J. et al. (2012) Use of eculizumab for atypical haemolytic uraemic syndrome and C3 glomerulopathies Nat. Rev. Nephrol. doi:10.1038/nrneph.2012.214

Prognosis Poor prognosis -mortality and ESRD is 53% at 3 years Risk of recurrent disease high -60% 90% subsequent graft loss despite plasma exchange De novo aHUS – poor outcome with plasma exchange Response from Eculizumab promising Genetic screening allows refined prediction of recurrence Living-related transplant contraindicated Combined liver kidney transplant may help CFH mutations are at highest risk of recurrence MCP mutations have low risk

What is the future for the patient? Hope for renal recovery If recovers, how much residual function? If no recovery, then chances of re-transplant? Options for dialysis? How long should she continue with eculizumab? Family/job adjustments

Learning points Post transplant TMA – serious cause of graft injury Wide differential diagnosis Rejection must be excluded (thus biopsy crucial) Prompt diagnosis is vital Important to discuss with experts

Elementary, my dear Watson… "How often have I said that when you have excluded the impossible whatever remains, however improbable, must be the truth." Sherlock Holmes

Figure 3 Diagnostic algorithm and therapeutic options for aHUS Zuber, J. et al. (2012) Use of eculizumab for atypical haemolytic uraemic syndrome and C3 glomerulopathies Nat. Rev. Nephrol. doi:10.1038/nrneph.2012.214

References Complement Inhibitor Eculizumab in Atypical Hemolytic Uremic Syndrome. Mache et al. CJASN Aug 2009 vol 4 no 8 1312-1316 Thrombotic microangiopathy and associated renal disorders. Barbour et al Nephrol Dial Transplant 2012, 27(7): 2673-2685. 3. Complement-mediated injury and protection of endothelium: Lessons from atypical haemolytic uraemic syndrome. Kerr and Richards. Immunobiology 2012 Feb 217 (2); 195-203 4. Outcome of renal transplantation in patients with non shiga toxin- associated haemolytic uraemic syndrome: prognostic significance of genetic background. Bresin et al. CJASN 2006; 1:88-99. 5. New insights into post renal transplant hemolytic uraemic syndrome. Nat Rev Nephrol 2010; 7:23-35 6. Treatment of atypical uraemic syndrome in the era of eculizumab Bachi et al Clin Kidney J 2012 5(1); 4-6

References 7. ASH 2012 haemotology education program 8. Symmers. Thrombotic microangiopathic haemolytic anaemia. Br Med J 1952 2:897-903. 9. Sommerfield et al. Thrombotic microangiopathy: case report and review of literature. JASN 1992;3: 35-41. 10. Bell et al. Improved survival in HUS/TTP syndrome New Eng J Med 1991: 325: 398-403 11. Zuber et al. Use of eculizumab for aHUS and C3 glomerulopathies. Nat Reviews Nephrology 2012 ; 8: 643-657. 12. Loirat et al. Plasma therapy in atypical HUS. Seminars in thrombosis and haemostasis 2010. Vol 36 (6). .