HUS with mutations in CFH and STEC infection treated with eculizumab in a 4-year-old girl

Shiga toxin-producing Escherichia coli infection as a precipitating factor for atypical hemolytic-uremic syndrome

BACKGROUND

Hemolytic uremic syndrome (HUS) is a thrombotic microangiopathy characterized by intravascular hemolysis. It can be classified as either typical, primarily caused by Shiga toxin-producing Escherichia coli (STEC) infection, or as atypical HUS (aHUS), which results from uncontrolled complement activation.

METHODS

We report the case of a 9-year-old boy with aHUS due to compound heterozygous complement factor H-related genes (CFHR) 1/3 and CFHR1-CFHR4 deletions, leading to the development of anti-complement factor H (CFH) autoantibodies. The patient presented nephrological and neurological thrombotic microangiopathy with STEC positivity. Additionally, we provide an extensive literature review of aHUS cases initially classified as typical.

RESULTS

A total of 11 patients were included, 73% of whom were pediatric. Kidney replacement therapy was required in 73% of patients. The recurrence rate was 55%. All cases were found positive for pathological variants of the complement system genes. The most commonly implicated gene was CFH, while the CFHR genes were involved in 36% of cases, although none exhibited anti-CFH autoantibodies. Anti-complement therapy was administered in 54% of cases, and none of the patients who received it early progressed to kidney failure.

CONCLUSIONS

STEC infection does not exclude aHUS diagnosis, and early use of anti-complement therapy might be reasonable in life-threatening conditions. Genetic testing can be helpful in patients with atypical presentations and can confirm the necessity of prolonged anti-complement therapy.

Constipation and hemolytic uremic syndrome

BACKGROUND

Shiga toxin-producing Escherichia coli (STEC) hemolytic uremic syndrome (HUS) classically presents with diarrhea. Absence of diarrheal prodrome increases suspicion for atypical HUS (aHUS). Inability to obtain a fecal specimen for culture or culture-independent testing limits the ability to differentiate STEC-HUS and aHUS.

CASE-DIAGNOSIS/TREATMENT

Our patient presented with abdominal pain and constipation, and evaluation of pallor led to a diagnosis of HUS. There was a complete absence of diarrhea during the disease course. Lack of fecal specimen for several days delayed testing for STEC. Treatment for atypical HUS was initiated with complement-blockade therapy. PCR-testing for Shiga toxin from fecal specimen later returned positive. Alternative complement-pathway testing did not identify a causative genetic variant or anti-Factor H antibody. A diagnosis of STEC-HUS was assigned, and complement-blockade therapy was stopped.

CONCLUSION

Diagnosis of aHUS remains a diagnosis of exclusion, whereby other causes of HUS are eliminated with reasonable certainty. Exclusion of STEC is necessary and relies on testing availability and recognition of testing limitations. Diarrhea-negative STEC-HUS remains a minority of cases, and future research is needed to explore the clinical characteristics of these patients.

Case report: Short-term eculizumab use in atypical HUS associated with Lemierre's syndrome and post-infectious glomerulonephritis

Atypical hemolytic uremic syndrome (aHUS) is a rare disease caused by genetic abnormalities, infections, autoimmune diseases, drugs, and malignancies. Anti-C5 monoclonal antibody eculizumab is the mainstay of treatment of aHUS caused by the genetic defects of the alternative complement pathway. However, the utility of eculizumab in non-genetic forms of aHUS and the timing of treatment discontinuation remain controversial. Here, we report successful short-term eculizumab use in two young adult patients with aHUS due to rare infectious and autoimmune etiologies: Lemierre's syndrome and post-infectious glomerulonephritis, respectively. Eculizumab was rapidly discontinued in both patients with no aHUS recurrence during long-term follow-up. Considering its favorable safety profile with appropriate meningococcal prophylaxis, eculizumab can be considered as a treatment option for non-genetic aHUS.