Concomitant oxidative haemolysis and methaemoglobinaemia following inhaled nitric oxide in a patient with G6PD deficiency.

We report the case of a man in his 50s who developed acute respiratory distress syndrome and right heart failure, necessitating intubation and initiation of inhaled nitric oxide (iNO) to decrease right ventricular afterload and improve the right heart function. The course was complicated by acute anaemia, with a diagnostic workup revealing methaemoglobinaemia and evidence of oxidative haemolysis indicated by blister and bite cells on peripheral blood film. The patient received conservative management, including successive red blood cell transfusion and gradual iNO weaning due to suspected glucose-6-phosphate dehydrogenase (G6PD) deficiency. Discontinuation of iNO led to the resolution of both oxidative haemolysis and methaemoglobinaemia. Subsequent enzymatic assay, conducted 4 months later, confirmed G6PD deficiency. This case highlights a rare instance of concurrent methaemoglobinaemia and oxidative haemolytic anaemia following iNO in a patient with underlying G6PD deficiency.