Differential Diagnosis of Landau-Kleffner Syndrome Versus Post Encephalitis Syndrome in a 13-year-old Boy With Autism Spectrum Disorder.

Landau-Kleffner syndrome (LKS) is a rare childhood neurological condition that causes developmental regression, loss of language skills and abnormal electroencephalogram (EEG) patterns. Its etiology is unknown. This report describes a case of a 13-year-old boy who at 3.5 years of age was bitten by a tick. Two months thereafter, he began losing previously acquired developmental and language skills, and developed seizures. The seizures subsided with valproic acid treatment, but the developmental delays persisted. Family history and disease progression reports obtained from the patient's father revealed that the patient displayed repetitive behaviors prior to the age of three. Clinical observation also showed the patient having numerous repetitive vocalizations and movements along with difficulty with switching sets. His developmental age at the time of presentation was determined to be 3 to 4 years of age. During the course of diagnostic testing, we were able to rule out tick-borne encephalitis (TBE) and rule in LKS in a premorbidly autistic child. This case describes the similarities between the three conditions and the diagnostic investigations used to arrive at a final diagnosis.