Autoantibodies against the calcium‐sensing receptor and cytokines in autoimmune polyglandular syndromes types 2, 3 and 4

OBJECTIVE: The frequency of autoimmunity against the parathyroid glands in patients with polyglandular autoimmunity that is not due to autoimmune polyendocrine syndrome type 1 (APS1) is unclear. To investigate this, the current study aimed to determine the prevalence of autoantibodies against parathyroid autoantigens the calcium-sensing receptor (CaSR) and NACHT leucine-rich-repeat protein 5 (NALP5) in a large group of patients with non-APS1 polyendocrine autoimmunity. Possible occult APS1 was investigated by cytokine autoantibody measurement and AIRE gene analysis. DESIGN, SUBJECTS, AND MEASUREMENTS: Subjects were 178 patients with APS2, 3 or 4, and 80 healthy blood donors. Autoantibodies against the CaSR, NALP5, and cytokines were measured by immunoprecipitation, radioligand binding assays, or ELISA, respectively. RESULTS: Four patient samples (2.2%), but none of the controls, were positive for CaSR autoantibodies. NALP5 autoantibodies were not detected in any participant. Eleven patients (6.2%) had cytokine autoantibodies, but none of the control samples was positive. None of the patients with cytokine autoantibodies had any known or novel mutations in the AIRE gene. CONCLUSIONS: The low prevalence of CaSR autoantibodies indicate a very low level of subclinical parathyroid autoimmunity in APS types 2, 3 and 4. In addition, autoantibodies against cytokines constitute an uncommon feature of non-APS1 polyglandular autoimmunity. This article is protected by copyright. All rights reserved.