These conditions are relatively uncommon.Conditions where the secondary polycythemia is not caused by physiologic adaptation, and occurs irrespective of body needs include:
Neoplasms – Renal cell carcinoma  or liver tumors, von Hippel-Lindau disease, and endocrine abnormalities including pheochromocytoma and adrenal adenoma with Cushings syndrome. People whose testosterone levels are high because of the use of anabolic steroids, including athletes who abuse steroids, or people on testosterone replacement for hypogonadism or transgender hormone replacement therapy, may develop secondary polycythemia. Blood doping - Secondary polycythemia can be induced by endurance athletes that take erythropoietin-stimulating agents, receive blood transfusions, and take other measures to increase their red blood cell mass in an effort to increase oxygen transport capacity. Altered oxygen sensing
Inherited mutations in three genes which all result in increased stability of hypoxia-inducible factors, leading to increased erythropoietin production, have been shown to cause erythrocytosis:
Chuvash erythrocytosis is an autosomal recessive form of erythrocytosis which is endemic in  patients from the Chuvash Republic in Russia. Chuvash erythrocytosis is associated with homozygosity for a C598T mutation in the von Hippel-Lindau gene (VHL), which is needed for the destruction of hypoxia-inducible factors in the presence of oxygen. Clusters of patients with Chuvash erythrocytosis have been found in other populations, such as on the Italian island of Ischia, located in the Bay of Naples. PHD2 erythrocytosis: Heterozygosity for loss-of-function mutations of the PHD2 gene are associated with autosomal dominant  erythrocytosis and increased hypoxia-inducible factors activity. HIF2α erythrocytosis: Gain-of-function mutations in HIF2α are associated with autosomal dominant erythrocytosis and pulmonary hypertension.
Relative polycythemia
Relative polycythemia is an apparent rise of the erythrocyte level in the blood; however, the underlying cause is reduced blood plasma (hypovolemia, cf. dehydration). Relative polycythemia is often caused by loss of body fluids, such as through burns, dehydration, and stress. A specific type of relative polycythemia is Gaisböck syndrome. In this syndrome, primarily occurring in obese men, hypertension causes a reduction in plasma volume, resulting in (amongst other changes) a relative increase in red blood cell count. Symptoms
Doctors say that patients may not experience in any notable symptom of PV until the late stages. Although vague, these symptoms might help patients get help in the early years of the progression. Severe headache
Dizziness, fatigue, and tiredness
Unusual bleeding, nosebleeds
Pain
Itchiness
Numbness or tingling in different body parts

Notable people
Polycythemia is linked to increased performance in endurance sports due to the blood being able to store more oxygen. It can also be linked to damage from smoking. Eero Mäntyranta, Finnish cross-country skier
Bob Newhart, American comedian

See also
Cytopenia, a decrease in blood cell count
Capillary leak syndrome, another cause of hemoconcentration

References


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