Hematology Question 29 Instructor

A 56 year old female is referred to clinic for a RBC count of 6.98 x 1012/L and hemoglobin of 190g/L with a platelet count of 750 x 109/L.

Differentiate between primary (bone marrow) and secondary causes of polycythemia.

Low Erythropoeitin Level High Erythropoeitin Level
Myeloproliferative Neoplasm: Polycythemia Vera Hypoxia: COPD, OSA, high altitude, smoker, right to left shunts
Cancer: hepatocellular carcinoma, renal cell carcinoma, cerebellar hemangioblastoma, pheochromocytoma, uterine myoma
Endocrine: Cushing’s, hyperaldosteronism
Medications: Epo, testosterone
Familial: Von Hippel Lindau mutation
Spurious: volume contraction

Her erythropoietin level is low at 2 IU/L and she has splenomegaly on exam. A JAK2 level is requested on the patient’s peripheral blood as there is suspicion of a myeloproliferative neoplasm.

What does the JAK2 level stand for?

Janus kinase 2 is a non-receptor tyrosine kinase, a genetic mutation identified on the short arm of chromosome 9p associated with constitutive tyrosine phosphorylation activity of the JAK-STAT pathway.

It is found in >96% of Polycythemia Vera patients, 50% of essential thrombocythemia, and 50% of myelofibrosis patients.

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