<s>[INST] Hello doctor, Is there an association between polycythemia and hemochromatosis? I have a high Hb of 18 and hematocrit of 51 %. I am a student and found to have incidental polycythemia. I tested for all myeloproliferative neoplasm and bone marrow biopsy is negative for MPN. However, I was tested to have hemochromatosis type 4, an autosomal dominant disease for which I am heterozygous. But my HCT and Hb are always high at 18.2. Please advise me. [/INST] Hello. Usually, in hemochromatosis, storage iron is increased, that is serum ferritin. So you can investigate with serum ferritin as well. If you have myeloproliferative neoplasm like polycythemia, then usually it can be clear from bone marrow study and JAK2 mutation. It comes under primary polycythemia case. You can rule out the secondary cause for polycythemia like lung disease, cardiac problem, high altitude, smoking, etc. Both conditions are different. </s>