Hemolytic Uremic Syndrome, Atypical, Susceptibility To, 5

A number sign (#) is used with this entry because susceptibility to the development of atypical hemolytic uremic syndrome-5 (AHUS5) can be conferred by mutation in the gene encoding complement component-3 (C3; 120700).

For a general phenotypic description and a discussion of genetic heterogeneity of aHUS, see AHUS1 (235400).

Clinical Features

Fremeaux-Bacchi et al. (2008) reported 11 probands with atypical HUS. Further pedigree analysis showed that 1 proband had 2 additional affected family members and another had 1 additional affected family member. Age at onset ranged from 8 months to 40 years. Most developed end-stage renal disease, and all had decreased serum C3. Six patients had undergone renal transplantation, 3 of whom had recurrence of the disease after transplantation.

Molecular Genetics

In 11 probands with atypical HUS, Fremeaux-Bacchi et al. (2008) identified 9 different heterozygous mutations in the C3 gene (see, e.g., 120700.0005-120700.0008). Five of the mutations resulted in a gain of function with resistance to degradation by MCP (120920) and CFI (217030), and 2 resulted in haploinsufficiency. Family history, when available, showed decreased penetrance.