Among IgG4‐RD mimetics, sarcoidosis (interstitial lung disease, adenopathy, granulomatous sialadenitis, increased serum CEA levels), ANCA vasculitis (interstitial lung disease, sinusitis, hypereosinophilia, glomerulonephritis, anti MPO or PR3 antibodies), neoplasia (altered general condition, adenopathy, pulmonary nodules or carcinomatous lymphangitis) and tuberculosis (pulmonary nodules, adenopathy and extra‐pulmonary involvement) must be considered systematically in case of pulmonary involvement. The gene discussed is PRTN3; the disease is interstitial lung disease.