Congenital methemoglobinemia

This code represents a rare, inherited blood disorder characterized by an abnormally high level of methemoglobin in the red blood cells, leading to impaired oxygen delivery to tissues. It is present from birth due to genetic defects affecting enzymes involved in methemoglobin reduction. Patients typically present with cyanosis despite normal arterial oxygen partial pressure.

Assign this code for patients diagnosed with a congenital form of methemoglobinemia, often identified in infancy or early childhood. Documentation should clearly state "congenital methemoglobinemia" or specify the genetic basis (e.g., NADH-cytochrome b5 reductase deficiency). This code is appropriate when the condition is the primary reason for the encounter or a significant co-morbidity.

• Differentiate from acquired methemoglobinemia (e.g., due to drug exposure), which is coded elsewhere.
• Ensure physician documentation explicitly states "congenital" to support this specific code.
• Consider additional codes for any associated symptoms or complications, if documented and clinically significant.