Congenital erythrocytosis with elevated erythropoietin level: An incorrectly set "erythrostat"?

Purpose: A child who was extensively evaluated for polycythemia is reported . Polycythemia, or erythrocytosis, is seen rarely in children. The mechanis ms for congenital and/or familial erythrocytosis are discussed. Patient and Methods: A 101/2-year-old white girl was referred for evaluatio n of polycythemia, which was detected incidentally during an emergency room visit for a febrile illness. She underwent extensive evaluation to determi ne the cause of the polycythemia. The literature was reviewed to determine the occurrence of congenital and/or familial erythrocytosis in children and its various causes. Results: Despite extensive evaluation, no specific cause of the erythrocyto sis could be determined in our patient. The erythrocytosis appeared to be s econdary to an inappropriately elevated serum erythropoietin concentration. Serum erythropoietin rose further after phlebotomy, suggesting nonautonomo us hypersecretion. After a review of the literature, we hypothesize that sh e had an inappropriate erythropoietin expression related to an abnormality in the renal oxygen-sensing mechanism governing erythropoietin synthesis. Discussion: A discussion of congenital and familial erythrocytosis is prese nted, and a review of the literature regarding the possible mechanisms caus ing erythrocytosis is included.