Hemolytic Uremic Syndrome Caused by Pneumococcal Infection Leads to Severe Illness in Young Children

Hemolytic uremic syndrome (HUS) caused by infection with pneumococcal bacteria leads to severe illnesswith a high rate of irreversible kidney damagein infants and young children, reports a study in the September issue of the Pediatric Infectious Disease Journal.

The new report is the largest series of Streptococcus pneumoniae-associated HUS (SP-HUS) among North American children since the introduction of routine vaccination against pneumococcal infection. A newer pneumococcal vaccine is likely to reduce the number of childhood SP-HUS cases, according to the new study, led by Dr. Ritu Banerjee of the Mayo Clinic in Rochester, Minn.

The researchers analyzed detailed information on 37 cases of SP-HUS occurring in the United States and Canada between 1997 and 2009. The cases were contributed by members of the Emerging Infections Network (EIN), which includes more than 259 pediatric infectious disease specialists throughout North America.

Hemolytic uremic syndrome is a disease causing destruction of red blood cells, which can lead to sudden (acute) kidney failure. Although HUS most commonly occurs as a reaction to childhood infections (such as with E. coli bacteria) causing diarrhea, it can result from pneumococcal and other infections as well.

Most cases of SP-HUS occurred in infants and young children: median age two years. Most had pneumonia and bloodstream infection (bacteremia) caused by pneumococcal bacteria; some had other infections such as meningitis. The children were severely ill, with 95 percent requiring treatment in the intensive care unit. Most needed mechanical ventilation, as well as surgical treatment for lung and chest infection.

Nearly three-fourths of patients required dialysis after developing kidney failure, which was irreversible in some cases. Of 30 children followed up for six months, nearly one-fourth were still on dialysis. Ten percent had received a kidney transplant.

Four children were left with permanent neurological abnormalities. One patient died, for a mortality rate of three percent.

In most of the children, infection occurred despite immunization with the PCV7 pneumococcal vaccine. Introduced in 2000, the PCV7 vaccine protects against seven major strains of pneumococcal bacteria. It has been highly effective in reducing the number of children with pneumonia, meningitis, and other invasive pneumococcal infections.

In the new study, almost all cases of SP-HUS were caused by pneumococcal strains not prevented by the PCV7 vaccineparticularly a newly emerged strain called serotype 19A. The recently introduced PCV-13 vaccine protects against six additional strains of pneumococcal bacteria, including serotype 19A.

The new study is one of the first to provide detailed information on SP-HUS in children after the introduction of PCV7. The pediatric infectious disease specialists contributing to the EIN are an important source of updated information on new trends in childhood infections.

Banerjee and coauthors hope their findings will increase awareness of this "rare and severe" childhood disease. They write, "Since nearly all serotypes associated with SP-HUS in this series are included in PCV13, vaccination with PCV13 has the potential to decrease the incidence of SP-HUS and its associated morbidity."