Delayed treatment and diagnostic challenges in differentiating multifocal acquired demyelinating sensory and motor neuropathy from lupus: a case report and literature review.

Background: Multifocal acquired demyelinating sensory and motor neuropathy (MADSAM) is a rare autoimmune-mediated inflammatory response with negative antibodies which causes demyelination of multiple peripheral nerves in an asymmetric distribution with both motor and sensory deficits. Diagnosis for MADSAM can be clinically challenging, relies on a combination of clinical and electrodiagnostic studies, and symptoms can overlap with other neurological conditions such as systemic lupus erythematosus (SLE). MADSAM is typically asymmetric, demyelinating, and limited to peripheral nerves, whereas SLE is systemic, more commonly axonal, and has vasculitic features. SLE is treated with steroids and immunosuppressants while MADSAM is treated with intravenous immunoglobulin (IVIG), steroids, or plasmapheresis. There is a good short-term prognosis for MADSAM with early treatment, but prognosis can worsen with delayed or inappropriate therapy. Case Description: We describe a case of a woman in her 50s who presented with progressive generalized weakness, weight loss, muscle atrophy, and numbness. She was initially diagnosed with SLE, but deteriorated despite treatment. A broad differential was considered which included SLE, paraneoplastic syndrome, chronic inflammatory demyelinating polyneuropathy (CIDP), amyotrophic lateral sclerosis (ALS), multiple sclerosis (MS), and Guillain-Barré syndrome. Serological studies, neuroimaging studies, nerve conduction studies, and electromyography (EMG) were performed. She was ultimately diagnosed with Lewis-Sumner syndrome, or MADSAM, a variant of CIDP. Conclusions: The case highlights the importance of understanding the various causes of weakness and neuropathy, particularly with an atypical presentation, to pursue the correct diagnostic tests and treatment. The case particularly focuses on the difference between MADSAM and SLE. There is significant clinical overlap between the two, and a misdiagnosis can delay effective treatment and worsen outcomes by allowing progression to more debilitating stages of the illness.