Acute measles encephalitis in adults: a case series in Vietnam

Acute measles encephalitis is a rare but severe complication of measles, particularly in adults, and carries high mortality and a substantial risk of neurological sequelae. Two mechanisms are recognized: direct viral invasion of the brain, termed primary measles encephalitis, and an immune-mediated postinfectious process, termed acute postinfectious measles encephalitis. Most descriptions come from children, and the presentation, pathogenesis, and management of adult disease remain poorly defined.

We describe four adults (aged 34-45 years) admitted with fever, rash, and altered mental status. Acute measles infection was confirmed by serum measles-specific IgM or measles virus RNA on real-time reverse-transcription PCR. Measles virus RNA was detected in cerebrospinal fluid in Case 1, indicating primary measles encephalitis. Case 2 was initially mistaken for varicella because of an atypical vesicular rash. Case 3 developed quadriparesis and sphincter dysfunction with electromyographic evidence of bilateral S1 radiculopathy; spinal imaging was not performed. Case 4 showed progressive thalamic and temporal lesions on magnetic resonance imaging. Cerebrospinal fluid pleocytosis ranged from 57 to 1046 cells/µL, and improved in most patients within 3 days of intravenous immunoglobulin. Two patients recovered without neurological sequelae, one survived with residual deficits, and one died from persistent cerebral injury complicated by multidrug-resistant septic shock.

In adults, acute measles encephalitis may reflect a biphasic process that combines direct viral neuroinvasion with immune-mediated inflammation, rather than a purely postinfectious phenomenon. Intravenous immunoglobulin was temporally associated with clinical and biochemical improvement, but its therapeutic role cannot be established from a case series and requires controlled study.