D74.0

Congenital methemoglobinemia is a rare genetic disorder characterized by the presence of an abnormal form of hemoglobin known as methemoglobin in the blood. This condition arises when the iron in hemoglobin is oxidized from its ferrous (Fe2+) to ferric (Fe3+) state, rendering it incapable of binding oxygen effectively. Patients with congenital methemoglobinemia typically present with cyanosis, a bluish discoloration of the skin, especially noticeable in the lips and extremities, due to reduced oxygen delivery to tissues. Symptoms may also include fatigue, shortness of breath, and in severe cases, neurological impairment. The disorder can be caused by mutations in genes responsible for hemoglobin production or by deficiencies in enzymes such as cytochrome b5 reductase, which normally reduces methemoglobin back to hemoglobin. Diagnosis is confirmed through blood tests measuring methemoglobin levels, and treatment may involve methylene blue administration or ascorbic acid in certain cases. Understanding this condition is crucial for medical coders, as it may be associated with other hematological disorders, necessitating careful documentation and coding.