Table 1.

An aetiological classification of HUS (see [1]). HELLP haemolysis, elevated liver enzymes, low platelets

Category	Characteristics
Level 1: aetiology advanced
1.i	Infection induced
	(a) Shiga and shiga-like toxin-producing bacteria; enterohaemorrhagic Escherichia coli, Shigella dysenteriae type 1, Citrobacter freundii
	(b) Streptococcus pneumoniae, neuraminidase and T-antigen exposure
1.ii	Disorders of complement regulation
	(a) Genetic disorders of complement regulation
	(b) Acquired disorders of complement regulation, e.g. anti-factor H antibody
1.iii	von Willebrand proteinase, ADAMTS13, deficiency
	(a) Genetic disorders of ADAMTS13
	(b) Acquired ADAMTS13 deficiency; autoimmune, drug induced
1.iv	Defective cobalamin metabolism
1.v	Quinine induced
Level 2: aetiology unknown
2.i	Human immunodeficiency virus (HIV)
2.ii	Malignancy, cancer chemotherapy and ionising radiation
2.iii	Calcineurin inhibitors and transplantation
2.iv	Pregnancy, HELLP syndrome and oral contraceptive pill
2.v	Systemic lupus erythematosus and antiphospholipid antibody syndrome
2 vi	Glomerulopathy
2.vii	Familial, not included in part 1
2.viii	Unclassified