CNTNAP2 and Isaacs syndrome: A study across three phenotypes with anti-CASPR-2 ABs (LE, Morvan, and Isaacs syndromes) found an HLA DRB1*11:01 association in ∼ 90% of limbic encephalitis cases.107, 108No association was found in the Morvan and Isaacs syndromes, suggesting distinct pathophysiological mechanisms.