Acute measles encephalitis in adults: a case series in Vietnam

BACKGROUND: 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. CASE PRESENTATION: 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. CONCLUSIONS: 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.