Clinical Features and Outcomes of Acute Intermittent Porphyria Presenting With Acute Quadriparesis: A Case Series and...

A retrospective case series of acute intermittent porphyria (AIP) presenting with acute quadriparesis is described with a focus on patterns of neuropathy and nerve conduction study findings.

Six patients with acute polyneuropathy were diagnosed with AIP on the basis of characteristic clinical findings, urine porphobilinogen levels, and pathogenic variants in the hydroxymethylbilane synthase gene. Vital function impairment, neuropathic patterns, serial changes in nerve conduction studies (NCS), and laboratory findings are reviewed.

A total of six patients with acute porphyric neuropathy were included. Patterns of weakness varied between upper and lower extremities. Three patients exhibited allodynia with preservation of large fiber sensory modalities in the acute polyneuropathy phase. Initial NCS revealed motor axonal polyneuropathy in four patients with sparing of motor conduction velocities and latencies. Relative sparing of tibial compound muscle action potential amplitudes is seen in two patients. Serial NCS revealed interval reduction of compound muscle action potential amplitudes in the upper extremity only in one patient and selective reduction of sensory nerve action potential amplitudes of the lower extremity in another patient. There were substantial delays in diagnoses, with all but one patient misdiagnosed as GBS. All but two patients required ambulation aids at last follow-up assessment.

The findings in this series show variability in neuropathic patterns and NCS changes over time in AIP presenting with acute polyneuropathy. Small fiber neuropathy and allodynia with sparing of large fiber sensory modalities may serve as a diagnostic clue guiding early recognition of AIP in patients presenting with acute polyneuropathy.