title: Congenital erythrocytosis.
abstract: BACKGROUND
  Congenital erythrocytosis is by definition present from birth. Patients frequently present in childhood or as young adults and a family history may be present. The erythrocytosis can be primary where there is a defect in the erythroid compartment of secondary where increased erythropoietin production produced due to the defect leads to an erythrocytosis.
  
  
  METHODS
  Primary causes include erythropoietin receptor mutations. Congenital secondary causes include mutations in the genes involved in the oxygen-sensing pathway and haemoglobins with abnormal oxygen affinity. Investigations for the cause include an erythropoietin level, oxygen dissociation curve, haemoglobin electrophoresis and sequencing for known gene variants.
  
  
  RESULTS
  The finding of a known or new molecular variant confirms a diagnosis of congenital erythrocytosis. A congenital erythrocytosis may be an incidental finding but nonspecific symptoms are described. Major thromboembolic events have been noted in some cases. Low-dose aspirin and venesection are therapeutic manoeuvres which should be considered in managing these patients.
  
  
  CONCLUSIONS
  Rare individuals presenting often at a young age may have a congenital erythrocytosis. Molecular investigation may reveal a lesion. However, in the majority, currently no defect is identified.
authors.affiliation: Department of Haematology, Belfast City Hospital, Queen's University Belfast, Belfast, UK.
authors.forename: M F
authors.initials: MF
authors.lastname: McMullin
mesh_terms: D000293:Adolescent; D001241:Aspirin / Q000627:therapeutic use; D002648:Child; D006801:Humans; D025202:Molecular Diagnostic Techniques / Q000379:methods; D018962:Phlebotomy; D011086:Polycythemia / Q000151:congenital* / Q000209:etiology / Q000628:therapy; D017467:Receptors, Erythropoietin / Q000235:genetics; D055815:Young Adult
chemical_list: D017467:Receptors, Erythropoietin; D001241:Aspirin
keywords: Congenital erythrocytosis; erythropoietin; erythropoietin receptor; high affinity haemoglobin; oxygen-sensing pathway