A Pediatric Case of Late Relapse of Neonatal Herpes Simplex Encephalitis in a 14-Year-Old

Herpes simplex encephalitis is the most common type of viral encephalitis. However, recurrence or relapse is rare. Late relapse, defined as recurrent active infection later than 3 months from the end of antiviral treatment, is even rarer. The following case illustrates the longest recorded idiopathic late relapse of herpes simplex encephalitis with biopsy-proven confirmation on histopathology. The literature suggests multiple mechanisms for relapse including latent reactivation, post-infectious autoimmune disease, and genetic predisposition. Regardless, untreated recurrent herpes simplex encephalitis has a high morbidity and mortality, and it is the only etiology of viral encephalitis with an effective anti-viral treatment. As such, it should remain an important consideration on the differential diagnosis of encephalitis for prompt recognition and timely management.