D70-D77: Other diseases of blood and blood-forming organs

D74: Methaemoglobinaemia

Methaemoglobinaemia is a unique group of conditions that affects how your blood carries oxygen through your body. Typically, red blood cells in your body carry and deliver oxygen, but in Methaemoglobinaemia, an abnormal form of hemoglobin called methemoglobin builds up. This methemoglobin isn't as effective at carrying oxygen, so not enough reaches your body's tissues. This condition can either be inherited, meaning you're born with it, or acquired, caused by exposure to certain chemicals and drugs. Typical symptoms include bluish or chocolate-brown colored skin, shortness of breath, fatigue, and rapid heart rate. Over time, if not treated, the condition can progress to more serious issues such as seizure or severe body-wide lack of oxygen.