Hemolytic uremic syndrome in an adolescent with Fusobacterium necrophorum bacteremia

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.

Atypical aHUS: State of the art

Tremendous advances in our understanding of the thrombotic microangiopathies (TMAs) have revealed distinct disease mechanisms within this heterogeneous group of diseases. As a direct result of this knowledge, both children and adults with complement-mediated TMA now enjoy higher expectations for long-term health. In this update on atypical hemolytic uremic syndrome, we review the clinical characteristics; the genetic and acquired drivers of disease; the broad spectrum of environmental triggers; and current diagnosis and treatment options. Many questions remain to be addressed if additional improvements in patient care and outcome are to be achieved in the coming decade.

Atypical hemolytic uremic syndrome

Hemolytic uremic syndrome (HUS) is a triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure. The atypical form of HUS is a disease characterized by complement overactivation. Inherited defects in complement genes and acquired autoantibodies against complement regulatory proteins have been described. Incomplete penetrance of mutations in all predisposing genes is reported, suggesting that a precipitating event or trigger is required to unmask the complement regulatory deficiency. The underlying genetic defect predicts the prognosis both in native kidneys and after renal transplantation. The successful trials of the complement inhibitor eculizumab in the treatment of atypical HUS will revolutionize disease management.

Systemic infections mimicking thrombotic thrombocytopenic purpura

The absence of specific diagnostic criteria, the urgency to begin plasma exchange treatment, and the risk for complications from plasma exchange make the initial evaluation of patients with suspected thrombotic thrombocytopenic purpura (TTP) difficult. Systemic infections may mimic the presenting clinical features of TTP. In the Oklahoma TTP-HUS (hemolytic-uremic syndrome) Registry, 1989-2010, 415 consecutive patients have been clinically diagnosed with their first episode of TTP; in 31 (7%) the presenting clinical features were subsequently attributed to a systemic infection. All 31 patients had diagnostic criteria for TTP; 16 (52%) had the complete "pentad" of microangiopathic hemolytic anemia, thrombocytopenia, neurologic abnormalities, renal failure, and fever. Four (16%) of 25 patients who had ADAMTS13 measurements had <10% activity; three patients had a demonstrable ADAMTS13 inhibitor. Compared with 62 patients with severe ADAMTS13 deficiency (<10%) who had no recognized alternative disorders, patients with systemic infections had more frequent fever, coma, renal failure, and the complete "pentad" of clinical features. Seventeen different infectious etiologies were documented. A systematic literature review identified 67 additional patients with a diagnosis of TTP or HUS and also a systemic infection. Among all 98 patients, infections with 41 different bacteria, viruses, and fungi were documented, suggesting that many different systemic infections may mimic the presenting clinical features of TTP. Initial plasma exchange treatment is appropriate in critically ill patients with diagnostic features of TTP, even if a systemic infection is suspected. Continuing evaluation to document a systemic infection is essential to determine the appropriateness of continued plasma exchange.

Is complement a culprit in infection-induced forms of haemolytic uraemic syndrome?

Haemolytic uraemic syndrome (HUS) accounts for the most common cause of childhood acute renal failure. Characterized by the classical triad of a microangiopathic haemolytic anaemia, thrombocytopaenia and acute renal failure, HUS occurs as a result of Shiga-toxin producing microbes in 90% of cases. The remaining 10% of cases represent a heterogeneous subgroup in which inherited and acquired forms of complement dysregulation have been described in up to 60%. Emerging evidence suggests that microbes associated with HUS exhibit interaction with the complement system. With the advent of improved genetic diagnosis, it is likely that certain cases of infection-induced HUS may be attributed to underlying defects in complement components. This review summarises the interplay between complement and infection in the pathogenesis of HUS.

Human infection with Fusobacterium necrophorum (Necrobacillosis), with a focus on Lemierre's syndrome

Human infection with Fusobacterium necrophorum usually involves F. necrophorum subsp. funduliforme rather than F. necrophorum subsp. necrophorum, which is a common pathogen in animals. Lemierre's syndrome, or postanginal sepsis, is the most common life-threatening manifestation. Tonsillitis is followed by septic thrombophlebitis of the internal jugular vein and then a septicemia with septic emboli in lungs and other sites. Recent evidence suggests that F. necrophorum can be limited to the throat and cause persistent or recurrent tonsillitis. F. necrophorum is unique among non-spore-forming anaerobes, first for its virulence and association with Lemierre's syndrome as a monomicrobial infection and second because it seems probable that it is an exogenously acquired infection. The source of infection is unclear; suggestions include acquisition from animals or human-to-human transmission. Approximately 10% of published cases are associated with infectious mononucleosis, which may facilitate invasion. Recent work suggests that underlying thrombophilia may predispose to internal jugular vein thrombophlebitis. Lemierre's syndrome was relatively common in the preantibiotic era but seemed to virtually disappear with widespread use of antibiotics for upper respiratory tract infection. In the last 15 years there has been a rise in incidence, possibly related to restriction in antibiotic use for sore throat.

Lemierre Syndrome: Two Cases and a Review

OBJECTIVES

Lemierre syndrome is usually caused by an acute oropharyngeal infection in previously healthy young adults, resulting in thrombophlebitis of the internal jugular vein, leading to metastatic septic embolization and bacteraemia. The usual organism is Fusobacterium necrophorum. Lemierre syndrome, not so long ago labeled as the "forgotten disease," is on the rise. Today with increasing antibiotic-resistant organisms, and decreasing awareness of the syndrome, subsequent re-emergence of this "forgotten disease" is becoming more common in clinical settings. Lemierre syndrome has significant morbidity. Cranial nerve complications associated with the condition have been increasingly diagnosed in the last few years. Looking back at literature on Lemierre syndrome, there have been review articles in medical and microbiology journals but rarely in otolaryngology journals. By presenting our cases we demonstrate the diverse presentations and severity of the illness.

METHODS

A review of the literature and a case report on two cases seen in our institution in the last year are presented. Each of these had varied presentations and neurologic complications-one developed 9th to 12th cranial nerve palsies and Horner syndrome, which have not been described in previous literature, and the other developed polyneuropathy and a frontal lobe infarct among other multisystem complications.

CONCLUSIONS

Diagnosis of Lemierre syndrome is not always straightforward as clinical features are variable and blood cultures are often negative. Awareness of the syndrome and a high degree of suspicion are needed.

Lemierre's syndrome: more than a historical curiosa

Lemierre's syndrome is a severe illness caused by the anaerobic bacterium, Fusobacterium necrophorum which typically occurs in healthy teenagers and young adults. The infection originates in the throat and spreads via a septic thrombophlebitis of the tonsillar vein and internal jugular vein. The ensuing bacteraemia is complicated by septic emboli to a range of sites such as lung, joints, and bones. Although rare, there is evidence of a resurgence in the condition in recent years, possibly associated with reduced use of antibiotic therapy for sore throats. The typical clinical picture is characteristic but many clinicians are unaware of the condition and diagnosis is often delayed with potentially fatal consequences.

Adult nondiarrhea hemolytic uremic syndrome associated with Shiga toxin Escherichia coli O157:H7 bacteremia and urinary tract infection

About 15% of children with Shiga toxin (Stx) producing Escherichia coli (STEC) primarily of serotype O157:H7, gastrointestinal infection, and watery or bloody diarrhea, may develop hemolytic uremic syndrome (D+ HUS). Usually D+ HUS is not complicated by bacteremia and patients recover spontaneously without antibiotic treatment. We report here an adult case of a STEC O157:H7 urinary tract infection complicated by bacteremia and HUS that was not preceded by diarrhea (D- HUS). Cases of D- HUS need to be carefully examined for foci other than the gastrointestinal tract, and patients with E coli bacteremia should receive early antibiotic treatment as would any patient with sepsis.