Pascual-Guàrdia et al. (42) published a rather large investigation (approximately 1,100 arterial or venous samples) in COVID-19 patients who in most cases were not critically ill (no mechanical ventilation, mean Hb concentrations of 13.3 ± 1.8 SD g/dl) and compared them to an even larger group of patients with pulmonary dysfunction caused by other illnesses. The gene discussed is GSTM1; the disease is COVID-19.