Mandl A, Burbelo PD, Di Pasquale G, et al. - Two cases of acquired parathyroid hormone (PTH) resistance resulting from the development of serum PTH type 1 receptor (PTH1R) autoantibodies, which block PTH binding and signaling, are presented herein.

• Both cases were linked with other autoimmune presentations.

• One case was related to atypical membranous glomerulonephritis.

• Presence of PTH1R-blocking IgG autoantibodies was revealed by in vitro binding and signaling assays.

• These autoantibodies were absent in serum samples from patients with other renal or autoimmune disorders.