Pure Motor Axonal Neuropathy Associated with Sjögren's Syndrome: A Rare Case Report

Peripheral nervous system involvement is a recognized extraglandular manifestation of Sjögren's syndrome (SjS), most commonly presenting as sensory or mixed sensorimotor axonal neuropathies. Pure motor axonal neuropathy is exceptionally rare in this context and may closely mimic anterior horn cell disorders, posing significant diagnostic and therapeutic challenges.

We report the case of a 47-year-old man with long-standing sicca symptoms who developed progressive, asymmetric motor weakness affecting all four limbs without sensory involvement. Neurological examination revealed predominantly left-sided motor deficits with preserved reflexes and normal sensory testing. Electrodiagnostic studies demonstrated a motor-predominant axonal neuropathy with reduced compound muscle action potential amplitudes and preserved sensory conduction. Serological testing showed high titers of anti-SSA antibodies, and minor salivary gland biopsy confirmed focal lymphocytic sialadenitis consistent with Sjögren's syndrome. Despite treatment with cyclophosphamide, plasma exchange, and high-dose corticosteroids, the patient showed no significant clinical improvement. Rituximab therapy was subsequently initiated; however, after four months of follow-up, motor weakness remained functionally limiting without meaningful neurological recovery.

This case describes a rare pure motor axonal neuropathy in a patient with Sjögren syndrome. The clinical and electrodiagnostic findings were compatible with Sjögren syndrome-associated motor axonal neuropathy after consideration of alternative causes. The limited response to immunosuppressive therapy highlights the potential importance of early recognition of this uncommon neurological manifestation.