It is broadly defined as acute or worsening respiratory compromise and/or acute or worsening pulmonary oedema during or up to 12 h after transfusion, cardiovascular changes (tachycardia, hypertension) not explained by the patient's underlying condition, evidence of fluid overload and supportive result of a relevant biomarker (e.g. brain natriuretic peptide) [1]. This evidence concerns the gene NPPB and pulmonary edema.