Autonomic and Small Fiber Neuropathy in Patients with Acute Hepatic Porphyrias

Introductionneurovisceral pain and autonomic symptoms are the initial and most common symptoms of acute hepatic porphyrias (AHPs) attacks. These symptoms also exist in between attacks. Autonomic dysfunction in AHPs has been evaluated previously, but systematic evaluation with modern methods has been lacking. In this study, we aimed to assess the prevalence of clinically diagnosed, electro-physiologically and pathologically confirmed autonomic/SFN in patients with AHPs.Materials and Methodseight genetically confirmed AHPs patients, who were enrolled in between attacks, underwent neurological examination quantified by the neuropathy impairment score; COMPASS-31 questionnaire to assess autonomic symptom severity; and skin biopsies to assess intra-epidermal nerve fiber density (IENFD) to test for SFN. To assess the autonomic functions, we tested the heart rate response to deep breathing, the Valsalva maneuver, head-up tilt test and performed the Quantitative Sudomotor Axon Reflex Test (QSART). The Composite Autonomic Severity Score (CASS) was calculated to quantify the impairment in different autonomic domains.Resultswe found evidence of SFN in the form of reduced IENFD or QSART responses and evidence of cardiovagal impairment in seven patients. Cardiovascular sympathetic impairment was present in three patients. COMPASS-31 and CASS scores ranged between 15-48/100 and 1-6/10, respectively, indicating a mild to moderate degree of autonomic impairment.Discussiona mild to moderate autonomic neuropathy involving different autonomic domains continues to exist in between AHPs attacks. Autonomic/small fiber neuropathy is invariably present in this patient population and offers a potential explanation for the chronic sensory neuropathic and autonomic manifestations.