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

2. 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

3. 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

4. 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

5. Changes in lab parameters

6. 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

7. Peripheral blood film

8. 10.8.15 Anuric AKI - Commenced on HD
Daily plasma exchange against octoplas
Transplant biopsy
CT chest/abdo/pelvis – no lymphadenopathy/masses
ADAMTS13 test – normal activity
On advice of Prof Goodship – commence eculizumab

9. Histology

10. Normal Glomerulus

11. Histology

12. Histology

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

14. 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

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

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

17. 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

18. 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

19. 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

20. 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

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

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

23. 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

24. 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

25. 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)

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

27. 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%

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

29. 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

30. 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 Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved. For permissions, please

31. 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: /nrneph

32. 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

33. 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

34. 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

35. 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

36. 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: /nrneph

37. References
Complement Inhibitor Eculizumab in Atypical Hemolytic Uremic Syndrome. Mache et al. CJASN Aug 2009 vol 4 no
Thrombotic microangiopathy and associated renal disorders. Barbour et al Nephrol Dial Transplant 2012, 27(7):
Complement-mediated injury and protection of endothelium: Lessons from atypical haemolytic uraemic syndrome. Kerr and Richards. Immunobiology 2012 Feb 217 (2);
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 (1); 4-6

38. References
7. ASH 2012 haemotology education program 8. Symmers. Thrombotic microangiopathic haemolytic anaemia. Br Med J : Sommerfield et al. Thrombotic microangiopathy: case report and review of literature. JASN 1992;3: Bell et al. Improved survival in HUS/TTP syndrome New Eng J Med 1991: 325: Zuber et al. Use of eculizumab for aHUS and C3 glomerulopathies. Nat Reviews Nephrology 2012 ; 8: Loirat et al. Plasma therapy in atypical HUS. Seminars in thrombosis and haemostasis Vol 36 (6). .