Tubular aggregate myopathy (TAM) and Stormorken syndrome (STRMK) are overlapping disorders affecting muscle, bones, spleen, and platelets. TAM/STRMK is caused by missense mutations in STIM1 and ORAI1, encoding key effectors of calcium homeostasis. Here we describe the first in-frame deletion in STIM1. Functional experiments in the cell model demonstrated that the deletion of 8 amino acids induces STIM1 overactivation, resulting in excessive extracellular calcium entry and major nuclear translocation of the calcium-dependent transcription factor NFAT. Overall, this work provides a molecular diagnosis for the affected family and sheds light on the role of the implicated amino acids in STIM1 regulation. (By Dr. Johann Böhm, https://jmg.bmj.com/content/early/2025/03/23/jmg-2024-110273 )