Polycythemia

Differential Diagnosis

• Primary
  • Polycythemia vera (PV) (JAK2 positive)
  • Myelofibrosis, CML, or CMML
  • Hypereosinophilic syndrome
• Secondary
  • Chronic hypoxia
    • Respiratory
      • Chronic CO poisoning, including smoking
      • Obstructive sleep apnea
      • IPF
      • Cystic fibrosis
      • Severe chronic lung disease
    • Cardiac
      • Congenital heart defects
      • Other causes of significant chronic shunt
  • Neoplasms (autonomous Epo production)
    • Renal cell carcinoma
    • Hepatocellular carcinoma (HCC), hemangioblastoma, pheochromocytoma, uterine leiomyomata
    • Cerebellar tumours
  • Decreased plasma volume
    • Hydrochlorothiazide (iatrogenic)
  • Others
    • Renal transplant, renal artery stenosis, cysts, hydronephrosis
    • Doping
    • Cobalt toxicity
    • POEMS syndrome

Investigations

• Repeat CBC to confirm
• JAK2, for myeloproliferative disorders such as polycythemia rubra vera (PRV)
• Erythropoietin level (Epo)
  • If elevated, suggests secondary cause
• Urinalysis r/o RCC
• Second-tier investigations:
  • Ultrasound abdo for splenomegaly and RCC
  • Bone marrow biopsy

Management

• If volume depleted, replace fluids and repeat CBC