A Case of Chronic Progressive Motor-Dominant Multiple Mononeuritis Associated with Primary Sjögren’s Syndrome

A 45-year-old female with a history of dry eyes presented with chronic progressive disturbance of her right finger extension, bilateral foot drops, and dysesthesia in the left lower leg. On admission, neurological examination revealed decreased tendon reflex in the right upper limb and bilateral lower limbs, and dysesthesia in the distal outer portions of the bilateral lower legs. Her vibration sensation was moderately diminished in both lower legs. Weakness ranging from moderate to severe was predominantly found in the muscles innervated by the radial (r > l), medial (r > l), ulnar (r > l), deep peroneal (r ≒ l), tibial (r < l), and medial planter nerves (r < l). Nerve conduction study showed asymmetrical axonal neuropathy, while chronic neurogenic changes were observed on needle electromyography. Cerebrospinal fluid analysis results were unremarkable, except for an elevated IgG index (1.53) and the presence of oligoclonal IgG bands. Seropositive anti-SS-A antibody and histological findings of the biopsied minor salivary gland, as well as the lack of other connective tissue disorders, indicated primary Sjögren syndrome (SjS). A left sural nerve biopsy showed inhomogeneous reductions in the myelinated fibers within fascicules, mild infiltration of CD8-positive T lymphocytes around small vessels, and no fibrinoid necrosis in the arteries. From these findings, the diagnosis of motor-dominant multiple mononeuritis associated with primary SjS was made. Therapy that comprised a single course of intravenous (IV) methylprednisolone (1 g for 3 days), followed by oral prednisolone (60 mg/day) with gradual tapering, resulted in no amelioration of her symptoms. She then received IV immunoglobulin (0.4 mg/kg/day for 5 days), which resulted in moderate improvement in the strength of several muscles and a reduction of CSF IgG index (0.89). A wide variety of peripheral nerve complications are documented in primary SjS. However, the present case is unique in the symptoms of chronic progressive, motor-dominant, multiple mononeuritic phenotype.