Nonmalignant hematologic conditions

• Acute blood loss
• Acute hemolytic anemia
• Iron deficiency anemia
• Treatment of vitamin B12 deficiency
• Rebound effect after treatment of ITP
• Rebound effect after ethanol-induced thrombocytopenia

Malignant conditions

• Metastatic cancer
• Lymphoma
• Rebound effect following use of myelosuppressive agents

Acute and chronic inflammatory conditions

• Rheumatologic disorders, vasculitides
• Inflammatory bowel disease
• Celiac disease
• Functional and surgical asplenia
• POEMS syndrome (osteosclerotic myeloma)

Tissue damage

• Thermal burns
• Myocardial infarction
• Severe trauma
• Acute pancreatitis
• Post-surgical period, especially post-splenectomy
• Coronary artery bypass procedures

Infections

• Chronic infections
• Tuberculosis

Exercise

Allergic reactions

Chronic renal disease

• Renal failure
• Nephrotic syndrome

Reaction to medications

• Vincristine
• Epinephrine, glucocorticoids
• Interleukin-1B
• All-trans retinoic acid
• Thrombopoietin, thrombopoietin mimetics
• Low molecular weight heparins (enoxaparin)

Proposed criteria for ET

• Sustained platelet count ≥450 x 10⁹/L*
• Bone marrow biopsy specimen showing proliferation mainly of the megakaryocytic lineage with increased numbers of enlarged, mature megakaryocytes; no significant increase or left-shift of neutrophil granulopoiesis or erythropoiesis
• Not meeting WHO criteria for PV^•, PMF^Δ, CML^◊, MDS^§ or other myeloid neoplasm
• Demonstration of JAK2 617V>F or other clonal marker, or in the absence of a clonal marker, no evidence for reactive thrombocytosis^¥