ANCA-related vasculitic neuropathy mimicking motor neuron disease.

Several conditions have been reported to mimic motor neuron disease (MND) and misdiagnosis remains a common clinical problem. Peripheral neuropathy is a classic feature of many vasculitic syndromes and in some patients it may be the only manifestation of vasculitis. We report a case of ANCA-related vasculitic neuropathy where the clinical presentation was suggestive of MND. A 42-year-old woman was admitted to our centre to confirm a diagnosis of MND made elsewhere. Clinical examination revealed postural tremor at the right hand, mild tongue atrophy with diffuse fasciculations and brisk tendon reflexes without other muscular weakness or atrophies. Electromyography demonstrated denervation in tongue and in the first dorsal interosseous of right hand ; motor evoked potentials disclosed normal central motor conduction time. Laboratory studies revealed only a mild increase of p-ANCA. A muscle biopsy showed a small inflammatory infiltrate around a vessel. The patient started high dosage of oral steroids. After one year of follow-up the patient suspended oral steroids, postural tremor of the right hand disappeared and tongue fasciculations were reduced. Vasculitis may mimic a MND, particularly in the absence of sensory involvement. Caution should be exercised in the clinical diagnosis of MND. Muscle biopsy is indicated in patient with atypical MND especially in those with an exclusive involvement of lower motor neuron.