Successful Treatment of Multifocal Demyelinating Sensory-Motor Neuropathy (Lewis-Sumner Syndrome) With Rituximab: A Case Report.

BACKGROUND Multifocal acquired demyelinating sensory-motor neuropathy (MADSAM) is recognized as a variant of chronic inflammatory demyelinating polyneuropathy. The primary characteristics of MADSAM include multifocal sensory loss and muscle weakness, which are frequently asymmetrical and predominantly affect the upper limbs. Involvement of the lower limbs is less commonly observed in MADSAM. CASE REPORT A 27-year-old female patient presented with recurrent numbness and weakness in her left lower limb was admitted to our hospital. Her medical history included episodes of left peripheral facial paralysis and lower-limb numbness and weakness, which had previously improved after short-term oral steroid therapy. In addition to motor and sensory peripheral nerve impairment in the left lower limb, the neurological examination revealed atrophy of the tongue muscle and a leftward deviation of the tongue. Cerebrospinal fluid examination and magnetic resonance imaging indicated no abnormalities. Electromyography suggested demyelination of motor and sensory nerves in the left lower limb. Sural nerve biopsy demonstrated demyelination changes and axonal degeneration. A diagnosis of multifocal sensory and motor neuropathy was considered, and the patient was administered corticosteroids and tacrolimus. As the condition progressed, electromyography showed gradual involvement of both lower limbs, leading to the consideration of MADSAM. Despite treatment with corticosteroids and tacrolimus, the patient experienced relapse. Rituximab was initiated, resulting in symptoms improvement and reduced recurrence without adverse events. CONCLUSIONS Corticosteroids, plasma exchange, and immunoglobulins have been demonstrated to be effective treatments for CIDP. In our MADSAM case, rituximab proved effective when the patient did not respond to corticosteroids and tacrolimus. We propose that rituximab may serve as an alternative option for patients with MADSAM.