Table 2.
Plasma concentration of C3, C4, CFH, CFI and CFB and expression of MCP in the various subgroups of atypical hemolytic uremic syndrome
| Protein level or expression | ||||||
|---|---|---|---|---|---|---|
| C4 | C3 | CFH | CFI | CFB | MCP | |
| CFH mutation | N | Normal (decreased) |
Normal (decreased) |
Normal | Normal (decreased) |
Normal |
| CFI mutation | N | Normal (decreased) |
Normal | Normal (decreased) |
Normal (decreased) |
Normal |
| MCP mutation | N | Normal (decreased) |
Normal | Normal | Normal | Decreased (normal) |
| CFB mutation | N | Decreased | Normal | Normal | Normal (decreased) |
Normal |
| C3 mutation | N | Decreased | Normal | Normal | Normal (decreased) |
Normal |
| THBD mutation | N | Normal or decreased |
ND | ND | ND | Normal |
| Anti-CFH Ab | N | Decreased (normal) |
Normal (decreased) |
Normal | Normal (decreased) |
Normal |
Very low C3 levels are observed in patients with homozygous CFH mutation (complete CFH deficiency) or compound heterozygous CFH mutation, and in patients with CFB or C3 gain-of-function mutations. In most of the other patients, C3 concentration is mildly decreased or normal. Undetectable CFH concentrations are observed only in patients with homozygous CFH mutation. Decreased CFH concentration can be observed in patients with heterozygous type 1 CFH mutation, and during flares of anti-CFH antibodies-HUS. Decreased C4 plasma levels have been reported in zero to a few % of patients of the various subgroups [18].
"Normal" and "decreased" without brackets means most frequently normal or decreased, within brackets means possible but not frequent. "Normal or decreased" without brackets means normal or decreased is equally frequent. CFH: factor H; CFI: factor I; MCP: membrane cofactor protein; CFB: factor B; THBD: thrombomodulin; Ab, antibodies. ND: not documented.