Autosomal dominant partial epilepsy with auditory features (ADPEAF) is a genetically heterogeneous disorder. Some patients exhibit mutations in the leucine-rich glioma inactivated (LGI1) gene. In an ADPEAF family, a novel mutation in the Lgi1 signal peptide is predicted to interfere with the protein cell sorting, resulting in altered processing. This finding suggests a loss-of-function mechanism for LGI1 gene mutations causing ADPEAF even if other mechanisms cannot be ruled out.