Apparent polycythaemia: diagnosis, pathogenesis and management

Abstract

The term “apparent polycythaemia” is applied to a group of patients who have a raised PCV (<0.51 in males, <0.48 in females) but a normal red cell mass (less than 25% above their predicted mean normal value). Some have additionally a marked reduction in plasma volume and can be defined as a subgroup: relative polycythaemia. Smoking, hypertension and to a lesser extent obesity, excessive alcohol, low‐dose diuretic therapy and hypoxaemia have all been associated with apparent polycythaemia but the mechanism is both uncertain and likely to be complex. This group of patients is unlikely to be uniform in pathogenesis and may well include some normal individuals. Investigation requires exclusion of factors associated with other types of polycythaemia. The possibility of an increased vascular occlusive risk is uncertain in these patients except at the higher PCV values. Reduction of PCV by venesection is sensible at PCV < 0.54 or where there is perceived to be an increased risk of vascular occlusion. The remaining patients should be managed by regular observation to detect further rise in PCV or evolution to absolute polycythaemia (raised red cell mass). In some, the PCV returns to normal.

Common genetic factors for hematological traits in Humans

“…[4][5][6][7][8] Studies comparing monozygotic and dizygotic twins have demonstrated that B50-90% of interindividual variance in WBC, RBC and PLT counts could be attributed to genetic components. 4,5 These heritabilities were observed only within healthy individuals, but genetic factors would also give some variance to disease abnormal data, which may get clinicians confused in interpretation of values.…”

Gaisbock's Syndrome: A Case Study

“…Stress related activation of the sympathetic nervous system has historically been linked with relative polycythemia [8]; in experimental animals, infusion of adrenalin and noradrenaline increases venous tone and causes mild reductions in plasma volume and small increases in PCV [9]. Although the evidence for an association of stress with relative polycythemia is somewhat tenuous [2], we suspect that it played a significant causative role in our patient's polycythemia.…”

“…Our patient had four risk factors for Gaisbock's syndrome -hypertension, diuretic therapy, physical and emotional stress, and obesity; of these, hypertension (particularly diastolic hypertension) appears to be the most significant contributor to the polycythemia of Gaisbock's syndrome [2]. In this regard, Emamian and associates studied 9,808 individuals with essential hypertension and found that they had spurious elevations in their hematocrits, hemoglobin levels, red cell counts, and mean corpuscular hemoglobin values [6].…”

“…Management should include tight control of hypertension, avoidance of diuretic therapy, smoking cessation, and, in obese individuals, institution of a vigorous weight loss regimen, which will have the added benefit of reducing the patient's risk for cancer, type 2 diabetes mellitus, ischemic heart disease, cerebrovascular disease, osteoarthritis of the hip and knees, and the metabolic syndrome. Venesection is rarely necessary, but should be considered if PCV levels are sufficiently elevated to place the patient at risk of thrombotic events (i.e., > 54 mL/dL) or if the patient is experiencing symptoms of cardiovascular ischemia [2,11].…”

“…In order of decreasing importance, risk factors for the development of Gaisbock's syndrome include male sex, hypertension, smoking, diuretic therapy, obesity, and emotional or physical stress. The polycythemia has been attributed to decreases in plasma volume, and may be associated with increases in blood viscosity and peripheral vascular resistance and a propensity to develop arterial and/or venous thromboses [1][2][3].…”