Isaacs Syndrome in A Patient with Positive CASPR2 And LGI1 Antibodies: A Case Report and Literature Review

Isaacs Syndrome (IS) is an autoimmune disease characterized by fasciculations, dysautonomia, and hyperactivity of muscle fibers due to hyperexcitability of the peripheral nerve system. Patients with IS often express voltage-gated potassium channels (VGKCs), contactin-associated protein 2 (CASPR2), and leucine-rich gliomainactivated protein (LGI1) antibodies. Slower rates of grouped fasciculation, known as myokymia, are a common presentation in IS patients. Recently, carbamazepine has been considered as the first-line treatment to alleviate the symptoms of IS patients. In this report, the authors present a case of a female patient with ramps and unintended movements in the abdomen and both lower limbs. She was diagnosed with IS after the detection of myokymia in the needle electromyography (EMG) and a positive paraneoplastic panel for CASPR2 and LGI antibodies. The patient is now symptom-free due to the administration of Carbamazepine, Gabapentin, and Baclofen. Additionally, due to her potential risk for solid tumors, she is under regular follow-up.