A Case Report of Systemic Lupus Erythematosus Presenting as Isolated Mononeuropathy Multiplex

Mononeuropathy multiplex is a pattern of progressive sensory and motor deficits in the distribution of two or more peripheral nerves. The differential for mononeuropathy multiplex includes vasculitis, autoimmune disorders, infectious diseases, sarcoidosis, amyloidosis, cryoglobulinemia, and paraneoplastic disease. We present a case of a 42-year-old woman with hypothyroidism who presented with 1 week of ascending numbness and weakness, persistent fevers, and 3 months of constant burning pain in both feet. Her neurologic exam was notable for asymmetric weakness, loss of sensation, and diminished reflexes of her lower extremities. Other than mild fever and tachycardia, there were no systemic exam findings. Her laboratory workup was significant for elevated inflammatory markers, positive ANA, anti-ribonucleoprotein, smooth muscle antibody, and lupus anticoagulant, high anti-dsDNA titers, and low complement levels. An MRI of her lumbar spine was negative for lumbosacral nerve root pathology. Cerebrospinal fluid studies demonstrated normal cell counts, glucose, and protein and no evidence of infection. An electromyography (EMG) and nerve conduction studies (NCS) demonstrated asymmetric involvement of multiple individual peripheral nerves. Given the patient's symptoms, asymmetric exam findings, laboratory results, and EMG/NCS findings, she was diagnosed with mononeuropathy multiplex secondary to systemic lupus erythematosus (SLE) and started on steroid and immunosuppressant therapy with symptomatic improvement. Overall, this case illustrates the unique presentation of mononeuropathy multiplex as the initial manifestation of SLE. The identification of this specific type of neuropathy may play a crucial role in the prompt diagnosis of SLE and timely initiation of treatment, preventing further complications of the disease.