In the North American cohort, all five patients with anti‐ACE2 IgM antibodies had proximal muscle weakness, had interstitial lung disease, were significantly more likely to receive pulse dose methylprednisolone (80% vs 30%, P = 0.043), and had worse forced vital capacity (median 59% predicted vs 78%, P = 0.056) compared with the anti‐ACE2‐IgM‐negative group. The gene discussed is CD40LG; the disease is interstitial lung disease.