POS1343 ABNORMAL ELECTROCHEMICAL SKIN CONDUCTANCE VALUES IN PATIENTS WITH AA AMYLOIDOSIS
Authors: S. Deshayes, R. Bourguiba, J. P. Haymann, L. S. F. Lea.Savey@aphp.Fr>;, A. Aouba, G. Grateau, S. Georgin-Lavialle
Journal: Annals of the Rheumatic Diseases (2021)

Background: Clinical manifestations are scarce in AA amyloidosis (AAA) and, contrary to other types of amyloidosis, involvement of the peripheral nervous system was rarely reported in AAA. However, the usual absence of hypertension despite chronic renal failure and the digestive involvement may be secondary to dysautonomia, but the autonomic nervous system has rarely been studied in AAA (1). Measure of the electrochemical skin conductance (ESC) is a simple and reproducible method to evaluate the function of eccrine sweat glands, which are innervated by small non-myelinated C fibers, and patients with AL and hereditary transthyretin amyloidoses show decreased ESC values (2,3). Objectives: To evaluate ESC values by Sudoscan in patients with AAA. Methods: Patients diagnosed as having AAA based on positive immunohistochemistry with an anti-serum amyloid A antibody followed at the national reference center for AAA in Tenon Hospital between July, 2017 and September, 2020, were routinely assessed for ESC with FDA approved Sudoscan (Impeto Medical, Paris, France). An ESC value above 60 microSiemens (µS) or 70 µS were considered normal for hands or feet, respectively. Categorical variables are reported as percentages and continuous variables are expressed as means±standard deviation. Correlations between age, body mass index (BMI), hemoglobin levels, C-reactive protein levels, estimated glomerular filtration rate using the Chronic Kidney Disease Epidemiology Collaboration equation (defined as 0 for dialysis patients) and ESC values were calculated using the nonparametric Spearman test. GraphPad Prism Version 7 software (GraphPad Software, San Diego, California, USA) was used for statistical analyses. A p-value &lt;0.05 was considered as statistically significant. Results: Overall, 32 patients (16 women) were included, with a mean age of 57.4±13.6 years and a mean BMI of 25.2±6.8 kg/m 2 . Six (19%) had diabetes mellitus, and 5 (16%) had a kidney transplantation. The main causes of AAA were: monogenic autoinflammatory diseases (n=11, 34%, including 9 patients with familial Mediterranean fever), chronic and/or recurrent infections (n=5, 16%), obesity (n=3, 9%) and undefined (n=3, 9%). The mean hands’ ESC values was normal at 65.5±21.1 µS, although 8 (25%) patients had ESC values below 60 µS, including 2 diabetic patients. In contrast, the mean feet’s ESC values was abnormal at 62.7±23.7 µS, including half of the patients with ESC values below 70 µS (2 diabetic patients). Eight patients had abnormal ESC values only for feet, and 1 had abnormal values only for hands. Apart from a significant correlation between feet and hands’ ESC values (p&lt;0.0001), only the estimated glomerular filtration rate was significantly associated with hands’ ESC values (p&lt;0.01). Conclusion: To our knowledge, this is the first study to assess ESC in AAA. Feet’s ESC values were moderately impaired in half of the patients with AAA. Therefore, this study reinforces the previously reported alterations in the autonomic nervous system in patients with AAA that should probably be searched for in these patients. In addition, the identification of an alteration of the ESC values cannot allow to distinguish the type of amyloidosis. References: [1]Nussinovitch U, Volovitz B, Nussinovitch M, Lidar M, Feld O, Nussinovitch N, et al. Abnormal heart rate variability in AA amyloidosis of familial Mediterranean fever. Amyloid 2011;18:206–10. [2]Montcuquet A, Duchesne M, Roussellet O, Jaccard A, Magy L. Electrochemical skin conductance values suggest frequent subclinical autonomic involvement in patients with AL amyloidosis. Amyloid 2020;27:215–6. [3]Fortanier E, Delmont E, Verschueren A, Attarian S. Quantitative sudomotor test helps differentiate transthyretin familial amyloid polyneuropathy from chronic inflammatory demyelinating polyneuropathy. Clin Neurophysiol 2020;131:1129–33. Disclosure of Interests: None declared