[Vasculitis confined to the peripheral nervous system: atypical clinical presentation]

Peripheral neuropathy is a common feature of many vasculitic syndromes. In some patients, the neuropathy may be the sole manifestation of vasculitis.

A 74-year-old lady complained of pain and weakness of the lower limbs. In her history, we noted right optic neuritis, monoclonal gammopathy and dyslipidemia treated by fenofibrate. Clinical examination showed proximal muscle strength deficit of lower limbs, with quadriceps femoral muscles atrophy. Muscle stretch reflexes were absent. There was no deficit in light touch and pain sensation, but proprioception was impaired. There was electromyographic evidence of myopathic impairment with abnormal spontaneous activity. Amplitude of the sensory action potentials was mildly reduced. Laboratory tests were normal. Fenofibrate was stopped, but the clinical symptoms increased. Four months later, another electrophysiological study showed a very reduced amplitude of sensory action potentials. Myopathic impairment was less severe. Nerve biopsy showed inflammation and necrosis of nerve arteries, which lead to the diagnosis of necrotizing vasculitis. A corticosteroid treatment was done. Six months later, clinical and electrophysiological improvement clearly appeared.

Histological lesions of vasculitis confined to the peripheral nervous system are those of classic polyarteritis nodosas. There is no systemic involvement nor biological abnormalities, which strengthens the role of nerve and muscle biopsy. The prognosis is good after corticosteroid treatment, which is not the case with systemic vasculitis.