[Childhood essential polycythemia: an unusual disorder].

We report the case of an 2-year-old boy presenting an essential polycythemia since birth, with details of the diagnostic procedures used and clinical course. Pediatric cases are very rare, and a secondary acquired polycythemia should be first investigated. Most causes of primary childhood polycythemia remains unknown. Erythropoietin (EPO) level may help to separate diseases with high EPO (Chuvash, or yet unclassified), or with normal/low EPO (congenital with truncation of the EPO receptor, polycythemia vera-Vaquez disease-, or currently with unknown mechanism).