Comprehensive Analysis of Complement Genes in Patients with Atypical Hemolytic Uremic Syndrome

Abstract

Background: Genetic defects in complement proteins reportedly contribute to the atypical hemolytic uremic syndrome (aHUS). Numerous genetic studies have been published in recent years, but limited data have been gathered from Asian countries. Methods: Genetic variants of 11 complement genes were analyzed in 23 Chinese patients with aHUS by high-throughput sequencing. The genotype-phenotype relationship in the Han population was evaluated and compared with the relationship that existed in other ethnicities. Results: We identified 20 causative mutations in complement genes, including 19 missense mutations and 1 splicing mutation. Six previously reported mutations, 6 mutations detected for the first time, and 8 rare polymorphisms were noted. Twelve out of 23 patients harbored complement mutations. Among the patients, one was a homozygote (Arg142Cys in CFHR3), and 4 carried combined mutations. Chinese patients have a similar prevalence of complement mutations as European, Japanese, and American patients. Complement factor H (CFH) mutations were common in aHUS in different ethnicities, but Chinese patients exhibited a higher percentage of complement factor B mutations than were found in European patients and a lower percentage of component 3 (C3) mutations than in Japanese patients. Compared with non-carriers, the aHUS patients carrying mutations had reduced C3 levels. In particular, patients with CFH mutations had a worse renal function than those with membrane cofactor protein mutations, a higher level of serum creatinine at the disease onset and a higher percentage of renal insufficiency during follow-up. Conclusions: Because complement genetic dysfunction has clinical significance in aHUS, a comprehensive assessment of variants is necessary for the proper management of aHUS patients in China.