Toll-like receptor 3 deficiency in autoimmune encephalitis post–herpes simplex encephalitis

The Toll-like receptor 3 (TLR3) pathway is a key component of the innate immunity that prevents replication of viruses in the CNS. Inborn errors of this pathway (TLR3-pathway deficiency), which includes defects in the genes TLR3 , UNC93B1 , TRIF , TRAF3 , TBK1 and IRF3 , occur in 10% of patients with herpes simplex encephalitis (HSE),1,2 and about 66% of these patients develop relapses of HSE.1 A recent study showed that 27% of patients with HSE develop autoimmune encephalitis (AE) in the weeks or months ensuing the infection.3 It is unknown whether TLR3-pathway deficient patients can also develop AE post-HSE. Here we report a patient with TLR3-pathway deficiency who developed HSE and a relapse of the viral infection followed by AE post-HSE, highlighting the fact that TLR3-pathway deficient patients should be carefully followed for both HSE relapses and AE. The authors thank Maria Rodes, Marta Munoz, Merce Alba, Eva Caballero, and Esther Aguilar for excellent administrative and technical support.