Targeted-genomic capture and high-throughput sequencing for genetic testing and new gene discovery in atypical hemolytic uremic syndrome

Abstract Abstract 4644 Background: Atypical hemolytic uremic syndrome (aHUS) is an ultra-rare disease characterized by microangiopathic hemolytic anemia (MAHA), thrombocytopenia and renal failure in the absence of Shiga toxin exposure. Dysregulation of the alternative pathway by mutations in complement regulatory proteins or antibodies to these proteins have been implicated in the pathogenesis of the disorder. Aims: We report the late onset of aHUS in association with heterozygous deletion of two genes, CFHR1 and CFHR3, and a mutation in CFH, c.497G>T, p.Arg166Leu. The latter mutation has not previously been reported with aHUS. Methods: A 20-year-old female whose past history was unremarkable with the exception of a spontaneous abortion 3 months earlier, presented to an emergency room with abdominal pain and bloody diarrhea three days after eating raw fish. Within 4 days of hospitalization she developed MAHA, thrombocytopenia and renal failure. Studies were negative for Shiga toxin and showed an ADAMTS13 level of 40%. A diagnosis of aHUS was made. Treatment was initiated with daily plasma exchange (PE) which was increased to twice daily for 6 weeks. Response was poor. After discontinuing PE, the patient was treated on an IRB-approved compassionate-use protocol with eculizumab 900 mg weekly for four weeks followed by 1200 mg every two weeks. Results: The patient responded slowly to eculizumab. PK values of eculizumab were sub-therapeutic at week 4. On week 5, she was switched to the maintenance dose of 1200 mg every two weeks, which resulted in a rapid normalization of her platelet count and LDH, with further improvement of her renal function and normalization of her mental status. The patient is doing well on continued eculizumab treatment. Genetic testing revealed a known copy-number variation (CNV), hemizygosity for CFHR1 and CFHR3, and a mutation in short consensus repeat (SCR) 3 of CFH, p.Arg166Leu. Summary/Conclusions: This patient presented with aHUS unresponsive to PE, but responsive to eculizumab treatment. Genetic testing of complement regulatory genes identified a known CNV and a mutation in CFH, p.Arg166Leu. This mutation lies in SCR3 of CFH, a region of the protein important for fluid-phase regulation of the C3 convertase. Although it has been seen in a rare case of dense deposit disease, it has not has not been reported with aHUS. This patient's poor response to PE suggests that additional genetic factors may be present in this patient that affected the course of disorder. Her slow response to eculizumab may have been due to third spacing of the drug secondary to hypoalbuminemia with anasarca as documented sub-therapeutic levels were present on week 4. When the dose was increased to 1200 mg every two weeks, the patient rapidly improved with resolution of the aHUS. Disclosures: No relevant conflicts of interest to declare.

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

American Journal of Nephrology ◽

10.1159/000445127 ◽

2016 ◽

Vol 43 (3) ◽

pp. 160-169 ◽

Cited By ~ 22

Author(s):

Tao Zhang ◽

Jianping Lu ◽

Shaoshan Liang ◽

Dachen Chen ◽

Haitao Zhang ◽

...

Keyword(s):

Hemolytic Uremic Syndrome ◽

High Throughput Sequencing ◽

Atypical Hemolytic Uremic Syndrome ◽

Disease Onset ◽

Factor H ◽

Chinese Patients ◽

Lower Percentage ◽

Complement Factor ◽

Missense Mutations ◽

Uremic Syndrome

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.

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Faculty Opinions recommendation of Genetic analysis of 400 patients refines understanding and implicates a new gene in atypical hemolytic uremic syndrome.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.734324478.793552635 ◽

2018 ◽

Author(s):

Santiago Rodríguez de Cordoba

Keyword(s):

Genetic Analysis ◽

Hemolytic Uremic Syndrome ◽

Atypical Hemolytic Uremic Syndrome ◽

Uremic Syndrome ◽

New Gene

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Eculizumab Is an Effective Treatment for Atypical Hemolytic Uremic Syndrome in Pediatric and Adult Patients with or without Identified Genetic Complement Mutations or Complement Factor H Autoantibodies

Blood ◽

10.1182/blood.v124.21.2789.2789 ◽

2014 ◽

Vol 124 (21) ◽

pp. 2789-2789

Author(s):

Spero R Cataland ◽

Thorsten Feldkamp ◽

Camille L. Bedrosian ◽

John Kincaid ◽

Enrico E. Minetti

Keyword(s):

Genetic Testing ◽

Hemolytic Uremic Syndrome ◽

Prospective Studies ◽

Atypical Hemolytic Uremic Syndrome ◽

Factor H ◽

Complement Factor H ◽

Complement Factor ◽

Renal Outcomes ◽

Genetic Abnormalities ◽

Uremic Syndrome

Abstract Introduction: Atypical hemolytic uremic syndrome (aHUS) is a rare, chronic disorder characterized by uncontrolled complement activation that results in life-threatening systemic thrombotic microangiopathy (TMA). Up to 79% of aHUS patients (pts) will have permanent renal damage, progress to end-stage renal disease, or die within 3 years following a clinical manifestation. Genetic abnormalities have been identified in up to 70% of pts with aHUS. Eculizumab (ECU) has previously been shown to be highly effective in the treatment of aHUS in 2 controlled, prospective studies (pts aged ≥12 y), and 1 retrospective study (pts aged <18 y). The purpose of this analysis was to evaluate the efficacy of ECU in adult and pediatric aHUS pts with or without identified genetic abnormalities in 2 additional prospective studies. Methods: This was a post hoc subgroup analysis of efficacy outcomes after 26 weeks based on the presence or absence of identified genetic abnormalities – mutations, complement factor H (CFH) autoantibodies, or polymorphisms – in 2 prospective studies conducted in either pediatric (<18 y) or adult pts (≥18 y) with aHUS. Results: In the pediatric and adult trials, respectively, 50% and 49% of pts had no identified genetic complement mutation or detectable CFH autoantibodies. There were no significant differences in demographics or baseline characteristics of pts with or without genetic abnormalities in either trial. ECU led to significant improvements in hematologic and renal outcomes regardless of mutation/CFH autoantibody status (Table). The change from baseline in platelet count and estimated glomerular filtration rate (eGFR) was statistically significant in mutation and no-mutation groups in both trials. In addition, of the pts in the mutation groups who were receiving PE/PI at baseline, 100% (6/6) of pediatric pts and 83.3% (15/18) of adult pts discontinued PE/PI after initiating ECU. In pts without an identified mutation on plasma exchange/plasma infusion (PE/PI) at baseline, 75% (3/4) of pediatric pts and 64.7% (11/17) of adult pts also discontinued PE/PI. For pts on dialysis at baseline in the mutation groups, 100% (5/5) of pediatric and 78.6% (11/14) of adult pts discontinued dialysis by 26 weeks, as did 66.7% (4/6) of pediatric and 90% (9/10) of adult pts in the no-mutation groups, respectively. Conclusions: Our analysis shows that significant improvements in hematological and renal outcomes, and rates of discontinuation of dialysis and PE/PI, occur in both pediatric and adult pts regardless of the presence or absence of identified complement abnormalities. Given that genetic testing can take several months to complete and that the absence of an identified mutation, CFH autoantibodies, or polymorphisms does not rule out aHUS, our results provide additional evidence for initiating ECU upon clinical diagnosis of aHUS, without the availability of genetic testing results. Disclosures Cataland: Alexion Pharmaceuticals: Consultancy, Speakers Bureau. Feldkamp:Alexion Pharmaceuticals: Consultancy, Honoraria, Speakers Bureau. Bedrosian:Alexion Pharmaceuticals: Employment. Kincaid:Alexion Pharmaceuticals: Employment. Minetti:Alexion Pharmaceuticals: Consultancy, Research Funding.

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