Secondary erythrocytosis is erythrocytosis that develops secondary to disorders that cause tissue hypoxia, inappropriately increased erythropoietin production, or increased sensitivity to erythropoietin.
Common causes of secondary erythrocytosis include
Less common causes include certain congenital disorders such as
Spurious erythrocytosis may occur with hemoconcentration (eg, due to burns, diarrhea, or diuretic use).
In patients who smoke cigarettes, reversible erythrocytosis results mainly from tissue hypoxia due to elevation of blood carboxyhemoglobin concentration; levels will normalize with smoking cessation.
Patients with chronic hypoxemia (arterial hemoglobin oxygen concentration < 92%), typically due to lung disease, right-to-left intracardiac shunts, renal transplantation, prolonged exposure to high altitudes Altitude Illness Altitude illness is caused by the decreased availability of oxygen at high altitudes. Acute mountain sickness (AMS), the mildest form, is characterized by headache plus one or more systemic... read more , or hypoventilation syndromes, often develop erythrocytosis. The primary treatment is to alleviate the underlying condition, but oxygen therapy may help, and phlebotomy Phlebotomy Polycythemia vera is a chronic myeloproliferative neoplasm characterized by an increase in morphologically normal red cells (its hallmark), but also white cells and platelets. Ten to 15% of... read more may decrease viscosity and alleviate symptoms. Because in some cases the elevated hematocrit is physiologic, phlebotomy should be limited to the extent necessary to relieve symptoms (in contrast to polycythemia vera, where the goal is to normalize the hematocrit).
Tumor-associated erythrocytosis can occur when renal tumors, cysts, hepatomas, cerebellar hemangioblastomas, or uterine leiomyomas secrete erythropoietin. Removal of the lesion is curative.
High oxygen–affinity hemoglobinopathies are very rare. This diagnosis is suggested by a family history of erythrocytosis; it is established by measuring the P50 (the partial pressure of oxygen at which hemoglobin becomes 50% saturated) and, if possible, determining the complete oxyhemoglobin dissociation curve. Standard hemoglobin electrophoresis may be normal and cannot reliably exclude this cause of erythrocytosis.
Tests done when isolated erythrocytosis is present include
Serum erythropoietin level is elevated in patients with hypoxia-induced erythrocytosis (or level is inappropriately normal for their elevated hematocrit) and in patients with tumor-associated erythrocytosis. Patients with elevated erythropoietin levels (and no indication of hypoxia) or microscopic hematuria should undergo abdominal imaging, central nervous system imaging, or both to seek a renal lesion or other tumor sources of erythropoietin.
P50 measures the affinity of hemoglobin for oxygen; a normal result excludes a high oxygen-affinity hemoglobinopathy (a familial abnormality) as the cause of erythrocytosis.
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Disease definition Secondary polycythemia is an elevated absolute red blood cell mass caused by enhanced stimulation of red blood cell production by an otherwise normal erythroid lineage that may be congenital or acquired (congenital secondary polycythemia and acquired secondary polycythemia; see these terms). Classification level: Group of disorders
Prevalence is unknown. Clinical features vary according to the origin of the disease but may include plethora or ruddy complexion, headache and tinnitus. The congenital form may be complicated by superficial or deep vein thrombophlebitis, or present with associated symptoms as in Chuvash erythrocytosis (see this term), or the course of the disease may be indolent. Patients with a specific sub-type of congenital secondary polycythemia, known as Chuvash erythrocytosis, present with lower systolic or diastolic blood pressure, venous varicosities, and vertebral body hemangiomas and may be complicated by cerebrovascular events or mesenteric thrombosis. The acquired form of secondary polycythemia may present with cyanosis, hypertension, clubbing of the fingers and toes and lethargy. Secondary polycythemia may be congenital and caused by defects in the oxygen sensing pathway due to autosomal recessive mutations in the VHL, EGLN1 and EPAS1 genes (3p26-p25, 1q42-q43 and 2p21-p16 respectively) which result in enhanced erythropoietin (EPO) production in hypoxic conditions, or by other autosomal dominant congenital defects including high oxygen-affinity hemoglobin and biphosphoglycerate mutase deficiency, which result in tissue hypoxia and a secondary erythrocytosis. Alternatively, secondary polycythemia may be acquired and caused by increased amounts of EPO. This may be due to tissue hypoxia that may be central and caused by pulmonary or cardiac disease or high altitude, or local and caused by hypoxia in the kidney such as renal artery stenosis. EPO production may be pathologic and caused by EPO secreting tumors such as renal cell cancer, hepatocellular carcinoma, cerebellar hemangioblastoma, meningioma and parathyroid carcinoma/adenoma (see these terms). In addition EPO may be administered deliberately to produce erythrocytosis and enhance performance. Diagnosis is based on evidence of increased total red blood cells and normal to high serum EPO levels. Secondary causes of erythrocytosis must be diagnosed individually and will require a comprehensive history. Differential diagnoses include polycythemia vera and primary familial polycythemia (see these terms), which can be excluded on the basis of low EPO levels and the presence of a mutation in the JAK2 gene (9p24) for polycythemia vera. There is little evidence to guide management of congenital secondary polycythemia. Phlebotomy or venesection may be of benefit, particularly in patients at increased risk of thrombosis. A target hematocrit (Hct) of 50% may be the most practical. In patients with no specific contraindication, low-dose aspirin may be of benefit. In acquired cases of secondary polycythemia, management is based on treating the underlying condition. Prognosis depends mainly on the associated disease in the acquired forms of secondary erythrocytosis and on the severity of thrombotic complications in the inherited forms such as in Chuvash erythrocytosis.
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Secondary polycythemia may be associated with
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