Dermatomyositis-associated sensory neuropathy: a unifying pathogenic hypothesis.

Neuropathy as extramuscular manifestation of dermatomyositis (DM) is controversial due to uncommon occurrence, heterogeneity of associated nerve pathology, and lack of unifying pathogenetic mechanism(s). We describe a patient with classic manifestations of DM and extramuscular manifestation of neuropathy. Nerve pathology showed deposits of terminal complement complex (C5b-9). Her examination showed mild proximal weakness, rash, and sensory impairment in fingertips, toes, and nose. EMG/NCS revealed irritable myopathy and mild sensory neuropathy. Muscle biopsy showed features suggestive of DM, including deposition of C5b-9. CK was elevated to 214 and ANA was positive at 1:160. Etiological work up for neuropathy, including diabetes, was negative. Sural nerve biopsy at light level revealed very mild large fiber sensory neuropathy. EM showed moderately severe involvement of small sensory fibers. Neuropathy may be an underrecognized manifestation of DM. Nerve pathology demonstrating complement-mediated damage could be a unifying mechanism of muscle and nerve injury.