Atypical hemolytic uremic syndrome (aHUS) is a rare, life-threatening thrombotic microangiopathy characterized by uncontrolled activation of the complement pathway, leading to microangiopathic hemolytic anemia, thrombocytopenia, and organ damage. The advent of complement inhibitors such as eculizumab and ravulizumab has transformed aHUS management, markedly reducing morbidity and mortality. However, long-term therapy presents challenges, including infection risks, economic burden, and the need for indefinite treatment. Discontinuing complement inhibition is a pivotal clinical decision that requires careful risk assessment to prevent relapse. Pathogenic gene variants in complement- regulating proteins, particularly CFH, CFI, MCP/CD46, and C3, significantly increase the risk of relapse, particularly within the first 3 to 12 months after cessation. Patients with multiple pathogenic variants or variants of uncertain significance exhibit heightened vulnerability, necessitating extended monitoring. Clinical predictors such as young age, prior kidney transplantation, and the presence of extrarenal manifestations further stratify relapse risk. Additionally, dynamic biomarkers such as elevated soluble C5b-9 at the time of discontinuation may signal imminent relapse. Comprehensive postdiscontinuation surveillance, including laboratory assessment of kidney function, hemolysis markers, and complement activity, is crucial for early relapse detection. Emerging strategies for personalized risk assessment, including pharmacogenomic profiling and biomarker-guided monitoring, may optimize therapeutic decision-making in aHUS. This review synthesizes current evidence on the long-term management of aHUS, focusing on strategies for anticomplement therapy discontinuation, relapse prediction, and individualized monitoring.

1.
Ávila
A
,
Cao
M
,
Espinosa
M
,
Manrique
J
,
Morales
E
.
Recommendations for the individualised management of atypical hemolytic uremic syndrome in adults
.
Front Md (Lausanne)
.
2023
;
10
:
1264310
.
2.
Loirat
C
,
Fakhouri
F
,
Ariceta
G
, et al
;
HUS International
.
An international consensus approach to the management of atypical hemolytic uremic syndrome in children
.
Pediatr Nephrol
.
2016
;
31
(
1
):
15
-
39
.
3.
Fakhouri
F
,
Fila
M
,
Provôt
F
, et al.
Pathogenic variants in complement genes and risk of atypical hemolytic uremic syndrome relapse after eculizumab discontinuation
.
Clin J Am Soc Nephrol
.
2016
;
12
(
1
):
50
-
59
.
4.
Noris
M
,
Remuzzi
G.
Atypical hemolytic-uremic syndrome
.
N Engl J Med
.
2009
;
361
(
17
):
1676
-
1687
.
5.
Hageman
GS
,
Hancox
LS
,
Taiber
AJ
, et al
;
AMD Clinical Study Group
.
Extended haplotypes in the complement factor H (CFH) and CFH-related (CFHR) family of genes protect against age-related macular degeneration: characterization, ethnic distribution and evolutionary implications
.
Ann Med
.
2006
;
38
(
8
):
592
-
604
.
6.
Veeranki
V
,
Meyyappan
J
,
Srivastava
A
, et al.
Long-term outcomes of anticomplement factor H antibody positive versus negative atypical hemolytic uremic syndrome
.
Indian J Nephrol
.
2025
;
35
(
3
):
402
-
409
.
7.
Fakhouri
F
,
Fila
M
,
Hummel
A
, et al.
Eculizumab discontinuation in children and adults with atypical hemolytic-uremic syndrome: a prospective multicenter study
.
Blood
.
2021
;
137
(
18
):
2438
-
2449
.
8.
Acosta-Medina
AA
,
Moyer
AM
,
Go
RS
, et al.
Complement gene variant effect on relapse of complement-mediated thrombotic microangiopathy after eculizumab cessation
.
Blood Adv
.
2023
;
7
(
3
):
340
-
350
.
9.
Ariceta
G
,
Fakhouri
F
,
Sartz
L
, et al.
Eculizumab discontinuation in atypical haemolytic uraemic syndrome: TMA recurrence risk and renal outcomes
.
Clin Kidney J
.
2021
;
14
(
9
):
2075
-
2084
.
10.
Chaturvedi
S
,
Dhaliwal
N
,
Hussain
S
, et al.
Outcomes of a clinician-directed protocol for discontinuation of complement inhibition therapy in atypical hemolytic uremic syndrome
.
Blood Adv
.
2021
;
5
(
5
):
1504
-
1512
.
11.
Caprioli
J
,
Castelletti
F
,
Bucchioni
S
, et al.
Complement factor H mutations and gene polymorphisms in haemolytic uraemic syndrome: the C-257T, the A2089G and the G2881T polymorphisms are strongly associated with the disease
.
Hum Mol Genet
.
2003
;
12
(
24
):
3385
-
3395
.
12.
Bernabéu-Herrero
ME
,
Jiménez-Alcázar
M
,
Anter
J
, et al.
Complement factor H, FHR-3 and FHR-1 variants associate in an extended haplotype conferring increased risk of atypical hemolytic uremic syndrome
.
Mol Immunol
.
2015
;
67
(
2, pt B
):
276
-
286
.
13.
Esparza-Gordillo
J
,
Goicoechea
de JE
,
Buil
A
, et al.
Predisposition to atypical hemolytic uremic syndrome involves the concurrence of different susceptibility alleles in the regulators of complement activation gene cluster in 1q32
.
Hum Mol Genet
.
2005
;
14
(
5
):
703
-
712
.
14.
Fremeaux-Bacchi
V
,
Fakhouri
F
,
Garnier
A
, et al.
Genetics and outcome of atypical hemolytic uremic syndrome: a nationwide French series comparing children and adults
.
Clin J Am Soc Nephrol
.
2013
;
8
(
4
):
554
-
562
.
15.
Fakhouri
F
,
Schwotzer
N
,
Frémeaux-Bacchi
V.
How I diagnose and treat atypical hemolytic uremic syndrome
.
Blood
.
2023
;
141
(
9
):
984
-
995
.
16.
Fakhouri
F
,
Zuber
J
,
Frémeaux-Bacchi
V
,
Loirat
C.
Haemolytic uraemic syndrome
.
Lancet
.
2017
;
390
(
10095
):
681
-
696
.
17.
Wijnsma
KL
,
Duineveld
C
,
Volokhina
EB
,
van den Heuvel
LP
,
van de Kar
NCAJ
,
Wetzels
JFM
.
Safety and effectiveness of restrictive eculizumab treatment in atypical haemolytic uremic syndrome
.
Nephrol Dial Transplant
.
2018
;
33
(
4
):
635
-
645
.
18.
Nandakumar
V
,
Braun
KMP
,
Willrich
MAV
.
Challenges for complement functional assays in the clinical laboratory: from test validation to clinical interpretation
.
J Immunol Methods
.
2025
;
537
:
113824
.
19.
Sridharan
M
,
Go
RS
,
Willrich
MAV
.
Clinical utility and potential cost savings of pharmacologic monitoring of eculizumab for complement-mediated thrombotic microangiopathy
.
Mayo Clin Proc Innov Qual Outcomes
.
2022
;
6
(
5
):
458
-
464
.
20.
Peffault de Latour
R
,
Brodsky
RA
,
Ortiz
S
, et al.
Pharmacokinetic and pharmacodynamic effects of ravulizumab and eculizumab on complement component 5 in adults with paroxysmal nocturnal haemoglobinuria: results of two phase 3 randomised, multicentre studies
.
Br J Haematol
.
2020
;
191
(
3
):
476
-
485
.
21.
Willrich
MAV
,
Ladwig
PM
,
Martinez
MA
, et al
;
Complement Alternative Pathway Thrombotic Microangiopathy (CAP-TMA) Disease Oriented Group at the Mayo Clinic
.
Monitoring ravulizumab effect on complement assays
.
J Immunol Methods
.
2021
;
490
:
112944
.
22.
Raina
R
,
Mangat
G
,
Hong
G
, et al.
Anti-factor H antibody and its role in atypical hemolytic uremic syndrome
.
Front Immunol
.
2022
;
13
:
931210
.
23.
Martin
M
,
Llorens-Cebria
C
,
León-Román
J
, et al.
Ex vivo C5b-9 deposition test to monitor complement activity in clinical and subclinical atypical hemolytic uremic syndrome and in transplantation-associated thrombotic microangiopathy
.
Kidney Int Rep
.
2024
;
9
(
7
):
2227
-
2239
.
24.
Mezö
B
,
Horváth
O
,
Sinkovits
G
,
Veszeli
N
,
Kriván
G
,
Prohászka
Z
.
Validation of early increase in complement activation marker sC5b-9 as a predictive biomarker for the development of thrombotic microangiopathy after stem cell transplantation
.
Front Med (Lausanne)
.
2020
;
7
:
569291
.
25.
AlZabali
S
,
AlBatati
S
,
Rahim
K
, et al.
A multicenter study evaluating the discontinuation of eculizumab therapy in children with atypical hemolytic uremic syndrome
.
Children (Basel)
.
2022
;
9
(
11
):
1734
.
26.
Duineveld
C
,
Glover
EK
,
Bouwmeester
RN
, et al.
Kidney transplantation in patients with aHUS: a comparison of eculizumab prophylaxis versus rescue therapy
.
Transplantation
.
2025
;
109
(
3
):
511
-
518
.
27.
Glover
EK
,
Smith-Jackson
K
,
Brocklebank
V
, et al.
Assessing the impact of prophylactic eculizumab on renal graft survival in atypical hemolytic uremic syndrome
.
Transplantation
.
2023
;
107
(
4
):
994
-
1003
.
28.
Nolasco
LH
,
Gushiken
FC
,
Turner
NA
, et al.
Protein phosphatase 2B inhibition promotes the secretion of von Willebrand factor from endothelial cells
.
J Thromb Haemost
.
2009
;
7
(
6
):
1009
-
1018
.
29.
Malpica
L
,
van Duin
D
,
Moll
S.
Preventing infectious complications when treating non-malignant immune-mediated hematologic disorders
.
Am J Hematol
.
2019
;
94
(
12
):
1396
-
1412
.
30.
Crew
PE
,
McNamara
L
,
Waldron
PE
,
McCulley
L
,
Christopher Jones
S
,
Bersoff-Matcha
SJ
.
Antibiotic prophylaxis in vaccinated eculizumab recipients who developed meningococcal disease
.
J Infect
.
2020
;
80
(
3
):
350
-
371
.
31.
Matsumura
Y.
Risk Analysis of eculizumab-related meningococcal disease in Japan using the Japanese Adverse Drug Event Report Database
.
Drug Healthc Patient Saf
.
2020
;
12
:
207
-
215
.
32.
Loirat
C
,
Frémeaux-Bacchi
V
.
Atypical hemolytic uremic syndrome
.
Orphanet J Rare Dis
.
2011
;
6
:
60
.
33.
Legendre
CM
,
Licht
C
,
Muus
P
, et al.
Terminal complement inhibitor eculizumab in atypical hemolytic-uremic syndrome
.
N Engl J Med
.
2013
;
368
(
23
):
2169
-
2181
.
34.
Halimi J-M,
Al-Dakkak
I
,
Anokhina
K
, et al.
Clinical characteristics and outcomes of a patient population with atypical hemolytic uremic syndrome and malignant hypertension: analysis from the Global aHUS registry
.
J Nephrol
.
2023
;
36
(
3
):
817
-
828
.
35.
Costigan
C
,
Raftery
T
,
Carroll
AG
, et al.
Neurological involvement in children with hemolytic uremic syndrome
.
Eur J Pediatr
.
2022
;
181
(
2
):
501
-
512
.
36.
Bogdan R-G,
Anderco
P
,
Ichim
C
, et al.
Atypical hemolytic uremic syndrome: a review of complement dysregulation, genetic susceptibility and multiorgan involvement
.
J Clin Med
.
2025
;
14
(
7
):
2527
.
37.
Noris
M
,
Remuzzi
G.
Cardiovascular complications in atypical haemolytic uraemic syndrome
.
Nat Rev Nephrol
.
2014
;
10
(
3
):
174
-
180
.
38.
Noris
M
,
Galbusera
M
,
Gastoldi
S
, et al.
Dynamics of complement activation in aHUS and how to monitor eculizumab therapy
.
Blood
.
2014
;
124
(
11
):
1715
-
1726
.
39.
Roumenina
LT
,
Jablonski
M
,
Hue
C
, et al.
Hyperfunctional C3 convertase leads to complement deposition on endothelial cells and contributes to atypical hemolytic uremic syndrome
.
Blood
.
2009
;
114
(
13
):
2837
-
2845
.
40.
Bouwmeester
RN
,
Duineveld
C
,
Wijnsma
KL
, et al.
Early eculizumab withdrawal in patients with atypical hemolytic uremic syndrome in native kidneys is safe and cost-effective: results of the CUREiHUS Study
.
Kidney Int Rep
.
2023
;
8
(
1
):
91
-
102
.
41.
Bouwmeester
RN
,
Engel
LJ
,
Altena
W
, et al.
Living with atypical hemolytic uremic syndrome in the Netherlands: patient and family perspective
.
Kidney Int Rep
.
2024
;
9
(
7
):
2189
-
2197
.
42.
Werner
H
,
Buder
K
,
Landolt
MA
,
Neuhaus
TJ
,
Laube
GF
,
Spartà
G.
Long-term health-related quality of life and psychological adjustment in children after haemolytic-uraemic syndrome
.
Pediatr Nephrol
.
2017
;
32
(
5
):
869
-
878
.
43.
Scully
M.
How to evaluate and treat the spectrum of TMA syndromes in pregnancy
.
Hematology Am Soc Hematol Educ Program
.
2021
;
2021
(
1
):
545
-
551
.
44.
Fakhouri
F
,
Scully
M
,
Provôt
F
, et al.
Management of thrombotic microangiopathy in pregnancy and postpartum: report from an International Working Group
.
Blood
.
2020
;
136
(
19
):
2103
-
2117
.
45.
Kelly
RJ
,
Höchsmann
B
,
Szer
J
, et al.
Eculizumab in pregnant patients with paroxysmal nocturnal hemoglobinuria
.
N Engl J Med
.
2015
;
373
(
11
):
1032
-
1039
.
46.
Rathbone
J
,
Kaltenthaler
E
,
Richards
A
,
Tappenden
P
,
Bessey
A
,
Cantrell
A
.
A systematic review of eculizumab for atypical haemolytic uraemic syndrome (aHUS)
.
BMJ Open
.
2013
;
3
(
11
):
e003573
.
47.
Sarno
L
,
Tufano
A
,
Maruotti
GM
,
Martinelli
P
,
Balletta
MM
,
Russo
D.
Eculizumab in pregnancy: a narrative overview
.
J Nephrol
.
2019
;
32
(
1
):
17
-
25
.
48.
Meena
P
,
Gala
R
,
Das
RR
, et al.
Kidney and pregnancy outcomes in pregnancy-associated atypical hemolytic uremic syndrome: a systematic review and meta-analysis
.
Medicine (Baltimore)
.
2025
;
104
(
5
):
e41403
.
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