Acquired methaemoglobinaemia induced by ingestion of plant growth promoter

Methaemoglobin is an altered state of haemoglobin wherein the iron moiety of haemoglobin is oxidised from its ferrous (Fe2+) to ferric (Fe3+) form. Methaemoglobinaemia is a condition characterised by increased methaemoglobin concentration in the blood that is greater than 1%. It is a potentially life-threatening condition as methaemoglobin hinders the delivery of oxygen to tissues, leading to hypoxia and tissue damage. Here we report a case of methaemoglobinaemia induced by self-poisoning with a plant growth promoter in India, which contained only organic substances and was free of any toxic substance. Prompt clinical suspicion and evaluation are critical to identify acquired methaemoglobinaemia because the condition is rare but potentially life-threatening. To summarise, methaemoglobinaemia is to be suspected with low oxygen saturation that does not improve on oxygen supplementation, disparity between spO2 and pO2 and chocolate brown coloured blood. It is treated with methylene blue, which reduces methaemoglobin to haemoglobin.