Because SERCA1 is only found in fast twitching (Type II) fibers,17 this phenotypical difference might be explained by the different percentages of fast‐twitch and slow‐twitch muscle fibers in the diaphragm of those species, respectively, 50:50 for humans, 24:76 for cattle, and 93:7 for mice.18, 19 One of our dogs was reported to experience apnea and cyanosis during severe episodes, which could be a consequence of diaphragmatic muscle stiffness. Here, ATP2A1 is linked to Cyanosis.