Neuromyotonia as an unusual neurological complication of primary Sjögren's syndrome: case report and literature review.

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.