[Acute intermittent porphyria with transient paresis and contracture. Evidence for initial myopathic dysfunction?]

A 70-year old man with acute intermittent porphyria had acute transient bibrachial paresis with moderate contracture of the involved muscles, which showed electrical silence in a conventional electromyographic investigation with surface electrodes placed over the contracted muscle belly (filter: 20 Hz-2 Hz, amplifier 50 microV). Slow finger movements were still possible and showed typical muscle-action potentials. This electroclinical correlation points to myopathic localized dysfunction, perhaps similar to rare case reports with patients having metabolic myopathy of McArdle's type.