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  • Updated 07.10.2023
  • Released 02.16.2013
  • Expires For CME 07.10.2026

Hemorrhagic shock and encephalopathy syndrome



Hemorrhagic shock and encephalopathy syndrome (HSES) is a rare disorder that primarily affects infants less than a year of age. It is often fatal despite intensive medical care, and rarely do those who survive escape severe neurologic impairment. There are no biological markers for HSES. The diagnosis rests on the recognition of its clinical and laboratory abnormalities. The hallmarks of the disorder are abrupt onset of high fever, shock, encephalopathy, seizures, coagulopathy, and renal and hepatic dysfunction. Laboratory abnormalities, including progressive decline in hematocrit and platelets and rising transaminases and creatine phosphokinase, are noted and tend to peak in the first 36 hours. Severe acidosis is typical at presentation. Onset tends to be at night to early morning hours and more often in the winter months. Overall incidence is unknown.

Key points

• Hemorrhagic shock and encephalopathy syndrome typically presents acutely in infants with extremely high fever (average 41°C), encephalopathy, and shock.

• Laboratory abnormalities of elevated creatine phosphokinase, transaminases, and severe acidosis are initially seen, and falling hematocrit and platelet counts occur during the first week. Laboratory abnormalities tend to normalize after a week.

• Neurologic manifestations are severe, with seizures and cerebral edema that correlate to outcome.

• No biological markers exist. Bacterial cultures are negative, and if viral studies are positive, the pathogen implicated does not typically cause a severe disease process.

• Death occurs in approximately 50% of patients, with severe neurologic impairment occurring in the majority of survivors.

Historical note and terminology

Hemorrhagic shock and encephalopathy syndrome (HSES) was originally described by Levin and colleagues (16). An initial report of 10 infants within a 12-month time frame suggested an epidemic (07), but this did not later appear to be the case. Surveillance for this syndrome was done in the mid-1980s to 1990s (02). It has been noted worldwide.

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