Electromyography (EMG) and nerve conduction studies (NCS) are appropriate for this patient with systemic lupus erythematosus (SLE) who most likely has mononeuritis multiplex. Mononeuritis multiplex is characterized by abnormal findings in the territory of two or more nerves in separate parts of the body. She has a foot drop with normal reflexes that suggests an injury to the peroneal nerve and wrist drop that suggests injury to the radial nerve. EMG/NCS would most likely document a peripheral neuropathy. Mononeuritis multiplex is highly specific for vasculitic disorders that affect the vasa vasorum or nerve vascular supply but can also occur in systemic inflammatory disorders such as SLE. The peroneal nerve is the most commonly affected nerve. Approximately 14% of patients with SLE have a peripheral neuropathy with the majority (60%) due to SLE. Risk factors for the development of SLE-associated peripheral neuropathy include moderate to severe disease and the presence of other neuropsychiatric SLE manifestations. Approximately two thirds of patients improve with more aggressive immunosuppression. EMG/NCS can identify a nerve (usually the sural nerve) that might be amenable to biopsy to document the vasculitis prior to aggressive immunosuppression.

Hydroxychloroquine can cause a neuromyopathy manifested by proximal muscle weakness and areflexia. Biopsy demonstrates vacuoles in the muscle cells. However, hydroxychloroquine has not been associated with mononeuritis multiplex.

SLE may rarely cause transverse myelitis, which is characterized by a rapidly progressing paraparesis associated with a sensory level. Autonomic symptoms, including increased urinary urgency, bladder and bowel incontinence, and sexual dysfunction, may be present. The patient has no symptoms suggesting transverse myelitis, and a spine MRI is not indicated.

A small-fiber neuropathy causes a burning pain in the extremities and has been associated with autoimmune diseases such as SLE but does not cause motor symptoms. Diagnosis is made by skin biopsy, which demonstrates a reduced density of small sensory nerve fibers in the skin.