Facial onset sensory motor neuronopathy (FOSMN) is a recently identified condition characterized initially by trigeminal sensory involvement followed by sensory propagation and motor neuronopathy. Few cases have been reported, and latest evidence points toward a neurodegenerative cause. We describe a 59-year-old female who presented a typical clinical picture of FOSMN over 10 years. Immunological investigations showed positive antinuclear antibodies and antibodies to extractable nuclear antigens (anti-Ro antibodies). A mild inflammatory infiltrate was found on salivary gland biopsy. Intravenous immunoglobulin therapy was effective in improving and then stabilizing this patient's condition. The pathophysiology of FOSMN remains uncertain, and this condition may be heterogeneous. An immune basis cannot be discounted in any given case, and suspected cases merit a trial of immunotherapy.