COMMENTARY

Hemolytic Uremic Syndrome in Children

William T. Basco, Jr., MD

Disclosures

November 17, 2011

Streptococcus pneumoniae-Associated Hemolytic Uremic Syndrome Among Children in North America

Banerjee R, Hersh AL, Newland J, et al; on behalf of the Emerging Infections Network Hemolytic-Uremic Syndrome Study Group
Pediatr Infect Dis J. 2011;30:736-739

Study Summary

Hemolytic uremic syndrome (HUS) is defined as the HUS clinical picture without diarrheal illness or without infection with toxin-producing Escherichia coli. Streptococcus pneumoniae is the most common cause of nondiarrheal HUS. Past reports of streptococcal HUS suggest that this form of HUS is more severe than E coli- associated HUS, with patients having higher rates of morbidity and mortality. Streptococcal HUS is usually triggered in patients with pneumonia or empyema. This study sought to improve on past reports by including cases from multiple medical centers, with the goal of better defining the clinical characteristics of this illness. Cases were identified through members of the Emerging Infections Network in 2009. They were asked to send information on cases of streptococcal HUS they had seen from 1997 to 2009. All patients met the Centers for Disease Control and Prevention's definition of HUS, including having microangiopathic hemolytic anemia, some degree of renal injury, and thrombocytopenia. In confirmed cases S pneumoniae was isolated from at least 1 body site, whereas in probable cases gram-positive diplococci were identified but not specifically speciated by culture. Information came from 15 members of the Network on 37 cases from 11 different centers in North America.

Most (92%) of the cases were confirmed by culture with the remaining 8% being presumed cases. The median age of the patients was 2 years, and 76% were up to date on their pneumococcal conjugate vaccine at the time they were diagnosed. Upon presentation, 89% were febrile, 92% had pneumonia, and 11% had meningitis. The median hemoglobin at time of admission was 10.2 g/dL; the median peripheral white blood cell count was 6.7 x 109/L, and the median circulating platelet count was 84,000.

Among the 34 patients from whom streptococcus was isolated, 24 of the samples were tested for pneumococcal serotype identification. Serogroup 19 was associated with 50% of the cases for which serotyping was completed. Only 1 patient had an isolate that was included in the 7-valent pneumococcal conjugate vaccine, but 92% of the patients were infected with serotypes included in the newer 13-valent pneumococcal vaccine. All but 2 patients were admitted to the intensive care unit, and 73% required dialysis at some point during their acute care. One child died and the median hospitalization was 22 days. The investigators were able to gather follow-up information for 30 patients, with a median follow time of 6 months. Only 40% of this group had neither renal nor neurologic damage. At time of follow-up, 13% were still experiencing neurologic deficits, 20% had proteinuria, and 30%-37% had either hypertension or elevated serum creatinine levels. Three children had received a kidney transplant. The investigators concluded that the clinical presentation of streptococcal HUS is severe; however, more than 90% of the cases are caused by pneumococcal serotypes that are included in the current 13-valent pneumococcal conjugate vaccine.

Viewpoint

This article is an epidemiologic report rather than a research study per se. In looking at the citations, this case series contains more than twice as many patients as in previous pneumococcal HUS studies. In addition, this case series was drawn from a more diverse regional area. The take-home message for most clinicians is to remember to consider pneumococcal HUS when patients present with HUS findings and that these patients may require even more aggressive therapy and support then their diarrheal HUS counterparts.

Abstract

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