Table 2.

Genetic Abnormalities Associated With aHUS

Gene	Abnormality	Main Effect	Frequency in aHUS
CFH	Heterozygous and (rarely) homozygous mutations mainly in the last 2 exons	Impaired cell-surface complement regulation	25%-30%
CFH/CFHRs	Nonallelic homologous recombinations	Impaired cell-surface complement regulation	3%-5%
CFHR1	Deletion and formation of anti-CFH antibodies	Impaired cell-surface complement regulation	5%-10%
CD46a	Heterozygous and (rarely) homozygous mutations	Reduced surface expression	8%-10%
CFI	Heterozygous mutations	Low cofactor activity	4%-8%
C3	Heterozygous mutations	Resistance to C3b inactivation, C3 convertase stabilization	4%-8%
CFB	Heterozygous mutations	C3 convertase stabilization	1%-4%
THBD	Heterozygous mutations	Reduced TAFI activation, reduced C3b inactivation	3%-4%
DGKE	Homozygous or compound heterozygous mutations	Protein truncation, proinflammatory and prothrombotic endothelial phenotype, increased endothelial apoptosis	2%-27% of infantile casesb

Abbreviations: aHUS, atypical hemolytic uremic syndrome; CFB, complement factor B; CFH, complement factor H; CFHR, complement factor H–related; CFI, complement factor I; DGKE, diacylglycerol kinase ε; MCP, membrane cofactor protein; TAFI, thrombin-activatable fibrinolysis inhibitor; THBD, thrombomodulin.

^aCD46 encodes MCP.

^bOnset of the disease before 1 to 2 years of age.