Polycythemia refers to an abnormal condition where hemoglobin (Hb), red blood cells (RBC), and hematocrit (HCT) in the blood circulation significantly exceed the normal range (neonates: Hb ≥ 220g/L, RBC > 7×10¹²/L, HCT > 65%; infants and children: Hb > 170g/L, RBC > 6×10¹²/L, HCT > 55%). Depending on its causes, it can be classified into:

1. Relative polycythemia: Seen in cases of hemoconcentration due to various causes and stress-induced polycythemia (e.g., splenic contraction).
2. Secondary polycythemia: Occurs in conditions such as cardiac or pulmonary hypoxia, high-altitude hypoxia, abnormal hemoglobin (e.g., HbM) disorders, and certain tumors (e.g., renal tumors, adrenal tumors, liver cancer, lung cancer, etc.), as well as excessive erythropoietin (EPO) production due to physical or chemical factors.
3. Primary polycythemia: Further divided into polycythemia vera and benign familial polycythemia. The former is a myeloproliferative disorder of unknown cause, while the latter is a benign autosomal dominant familial disorder.
4. Neonatal polycythemia: Seen in cases of twin-to-twin transfusion, fetomaternal transfusion, intrauterine hypoxia, and certain congenital genetic disorders.

bubble_chart Clinical Manifestations

1. Relative and secondary polycythemia: Clinically relatively common, with identifiable primary disease or cause. After removing the disease cause, polycythemia can return to normal.
2. Polycythemia vera: Patients are mainly adults, and it is extremely rare in children. The main manifestations are purplish-red skin and mucous membranes, most obvious in the cheeks, lips, conjunctiva, palms, etc. The spleen is often enlarged, and patients are prone to phlebitis and venous thrombosis.

bubble_chart Auxiliary Examination

1. Secondary polycythemia is primarily characterized by hemoglobin, red blood cell count, and hematocrit levels significantly exceeding normal values.
2. In polycythemia vera, in addition to the aforementioned erythroid changes, the following manifestations may also be present: increased white blood cells and platelets (>300×10⁹/L), increased blood volume, blood viscosity may increase by 4 to 5 times, arterial oxygen saturation is normal, marked hyperplasia of all three bone marrow lineages (especially the erythroid lineage), decreased or absent intracellular and extracellular iron, and a neutrophil alkaline phosphatase score >100.

bubble_chart Treatment Measures

(1) Secondary polycythemia

The main treatment is to address the primary disease and eliminate the disease cause. Venesection may be performed if necessary, which can provide temporary relief.

(2) Polycythemia vera

The following treatments may be used:

1. Venesection therapy: Generally, 5–10 ml/kg of blood is removed each time, repeated every 3–5 days until the HCT < 50%，RBC < 6×10¹²/L. Low-molecular-weight dextran may be administered after venesection to prevent thrombosis.
2. Chemotherapy: Suitable for patients with excessively high platelet counts (over 800×10⁹/L), those whose symptoms do not improve with frequent venesection, those with significant splenomegaly or hepatomegaly, and those with excessively high levels of uric acid in blood or urine. Commonly used drugs include cyclophosphamide, busulfan, chlorambucil, and fortune plumyew twig and leaf alkaloids.
3. ³²P therapy: Used after several venesections, with the same indications as above. The dosage is 2–3 millicuries administered orally or intravenously once. If no improvement is observed after 3 months, a half-dose may be given once more. Typically, 1–2 doses can achieve remission, but attention should be paid to the bone marrow suppression side effect.