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.
