Primary Sjögren\'s syndrome (PSS) is a systemic autoimmune disorder characterized by chronic inflammation of exocrine glands such as the lachrymal and salivary glands, leading to xerophthalmia and xerostomia. Neurological manifestations are sometimes found in patients with PSS. A variety of neurological complications has been reported in patients with PSS, and both the central nervous system (CNS) and peripheral nervous system (PNS) can be involved in PSS. Several forms of neuropathy, including polyneuropathy, cranial neuropathy, and multiple mononeuropathy, are often seen in PSS patients. Herein, we report for the first time typical neuromyotonia (NMT) symptoms appearing in a patient with PSS. Neuromyotonia is a rare disorder caused by the hyperexcitability of peripheral nerves, causing spontaneous and continuous muscle contraction. We provide an overview of the literature relating to neurological involvement in PSS, and the etiology of acquired NMT. We also discuss the existence of contactin-associated protein-like 2 (Caspr2) antibodies in NMT patients.

This is a case report of Isaacs\' syndrome in dermatomyositis. The patient presented with proximal muscle weakness, rash, elevated muscle enzyme, myopathic electromyograph and typical muscle biopsy. Ultimately he developed typical symptoms of Isaacs\' syndrome which is an autoimmune channelopathy from voltage gated potassium channel antibody (anti-VGKC) leading to dysfunction of axonal discharge at neuromuscular junctions. It shares some similar characteristics with dermatomyositis such as autoimmunity, its association with malignancy and the response to treatment.

Isaacs syndrome is a peripheral nerve hyperexcitability (PNH) syndrome that presents as continuous motor activity. Clinical findings include cramps, fasciculations, and myokymia. Electrodiagnosis plays a key role in diagnosis by demonstrating after-discharges on nerve conduction studies, and fasciculation potentials, myokymic discharges, neuromyotonic discharges, and other types of abnormal spontaneous activity on needle examination. Etiopathogenesis involves the interaction of genetic, autoimmune, and paraneoplastic factors, which requires a broad-ranging evaluation for underlying causes. Initial treatment is symptomatic, but immune therapy is often needed and can be effective. The purpose of this review is to describe the syndrome and its pathogenesis, assist the reader in evaluating patients with suspected Isaacs syndrome and distinguishing it from other disorders of PNH, and suggest an approach to management, including both symptomatic and immunomodulating therapy.