Polyneuropathy with endoneurial immune complex deposition as the first manifestation of systemic lupus erythematosus.

A 72-year-old male presented with progressive sensorimotor polyneuropathy. Later weight loss, proteinuria and deteriorating renal function were noted. The electrophysiological examinations revealed extensive, symmetrical demyelinating and axonal polyneuropathy. Frozen sections obtained from sural nerve biopsy sample showed the presence of immune complexes and complements in the walls of the epi- and endoneurial blood vessels, and perineurium suggestive of systemic lupus erythematous (SLE). IgG and Clq deposits were also present along the basement membranes of Schwann cells. The electron microscopy confirmed the presence of immune complex deposition. Diagnosis of SLE was proven by positive serology (anti-nuclear antibodies, anti-Sm, anti-RNP, anti-double-stranded DNA) and renal biopsy showing membranous lupus nephritis with extensive immune complex deposition in the tubular basement membranes. Despite combined immunosuppressive treatment for 10 months, the patient died of complications of generalized immune complex vasculitis. The manifestation of SLE in elderly patients, especially in males, is very rare. Moreover, the polyneuropathy is an unusual initial symptom of SLE. Immune complex deposition in Schwann cell basement membrane probably plays an important role in the pathomechanism of sensorimotor polyneuropathy in SLE.