Diagnosis

The diagnosis of PV can be made with great confidence if the proposed modified criteria are used, as shown in Table 48.1.7 Despite its inclusion in Table 48.1, the need for routine red cell mass determination

Table 48.1 Proposed modified criteria for the diagnosis of polycythemia vera

A1 Raised red cell mass (>25% above mean normal predicted value, or PCV >0.60 in males or 0.56 in females)

A2 Absence of cause of secondary erythrocytosis

A3 Palpable splenomegaly

A4 Clonality marker, i.e., acquired abnormal marrow karyotype

B1 Thrombocytosis (platelet count >400 X 109/L)

B2 Neutrophil leucocytosis (neutrophil count >10 X 109/L; >12.5 X 109/L in smokers)

B3 Splenomegaly demonstrated on isotope or ultrasound scanning

B4 Characteristic BFU-E growth or reduced serum erythropoietin

A1 + A2 + A3 or A4 establishes PV; A1 + A2 + two of B establishes PV .

Table 48.2 Common causes of secondary erythrocytosis

Congenital

Mutant high-oxygen-affinity hemoglobin Congenital low 2,3-diphosphoglycerate Autonomous high erythropoietin production

Acquired

Arterial hypoxemia (high altitude, cyanotic congenital heart disease, chronic lung disease) Other causes of impaired tissue oxygen delivery (smoking) Renal lesions (renal tumors, cysts diffuse parenchymal disease, hydronephrosis, renal artery stenosis, renal transplantation)

Endocrine lesions (adrenal tumors) Miscellaneous tumors (cerebellar hemangioblastoma, uterine fibroids, bronchial carcinoma) Drugs (androgens)

Hepatic lesions (hepatoma, cirrhosis, hepatitis)

is controversial. Its major utility is in the evaluation of border line elevations of hematocrit. It is important to exclude secondary causes of erythrocytosis (Table 48.2) related to increased erythropoietin, which may be physiologically appropriate (e.g., high altitude, smoking) or physiologically inappropriate (e.g., erythropoi-etin-secreting tumors). Thus, the measurement of serum erythropoietin is helpful in the differential diagnosis. PV patients have low or normal erythropoietin production secondary to a negative feedback mechanism. In contrast, patients with secondary erythrocyto-sis typically have elevated erythropoietin levels.

0 0

Post a comment