Familial erythrocytosis

This diagnosis code signifies a rare, inherited disorder characterized by an abnormally high red blood cell count (erythrocytosis) due to a genetic predisposition. Unlike secondary erythrocytosis, this condition is not caused by an underlying disease or external factors, but rather by intrinsic defects in red blood cell production or regulation.

Assign this code when documentation clearly indicates a diagnosis of familial erythrocytosis, often supported by a family history of the condition and genetic testing results. It is appropriate for patients presenting with chronic, unexplained erythrocytosis where other causes have been ruled out.

• Differentiate from secondary erythrocytosis (e.g., due to hypoxia, renal disease) which would be coded with a more specific underlying condition.
• Ensure documentation specifies "familial" or "hereditary" to support the use of this code, as opposed to other forms of erythrocytosis.
• Remember the Excludes1 note: do not code this alongside hereditary ovalocytosis (D58.1) as these are mutually exclusive conditions.