Transcobalamin II deficiency

This code represents a rare, inherited metabolic disorder characterized by the body's inability to transport vitamin B12 (cobalamin) into cells due to a deficiency in transcobalamin II, the primary B12 transport protein. This leads to functional B12 deficiency despite normal or elevated serum B12 levels, impacting hematopoiesis and neurological function.

Use this code for patients diagnosed with transcobalamin II deficiency, often presenting with megaloblastic anemia, developmental delay, or neurological symptoms in infancy or early childhood. Documentation should confirm the diagnosis through genetic testing or specific biochemical assays demonstrating low transcobalamin II levels and impaired cellular B12 uptake.

• Differentiate from other B12 deficiencies (e.g., pernicious anemia, dietary deficiency) which have distinct codes.
• Ensure documentation specifies "transcobalamin II deficiency" rather than a general B12 deficiency.
• Consider sequencing this code as the primary diagnosis when it is the reason for the encounter, especially for diagnostic workup or management of this specific condition.