Polycythemia refers to an abnormal condition in which 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%). Based on its causes, it can be classified into:

1. Relative polycythemia: seen in various conditions causing hemoconcentration and stress-induced polycythemia (e.g., splenic contraction).
2. Secondary polycythemia: occurs due to cardiac or pulmonary hypoxia, high-altitude hypoxia, abnormal hemoglobin (e.g., HbM) disorders, certain tumors (e.g., renal tumors, adrenal tumors, liver cancer, lung cancer, etc.), and excessive erythropoietin (EPO) production caused by 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 with a favorable prognosis.
4. Neonatal polycythemia: observed 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: mainly characterized by hemoglobin, red blood cell count, and hematocrit significantly exceeding normal values.
2. 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 4-5 times, normal arterial oxygen saturation, marked hyperplasia of all three bone marrow lineages (especially the erythroid lineage), decreased or absent intracellular and extracellular iron, and neutrophil alkaline phosphatase score >100.

bubble_chart Treatment Measures

1. Secondary polycythemia: The main treatment is to address the underlying disease and eliminate the disease cause. Venesection may be performed when necessary, which can provide temporary relief.
2. Polycythemia vera: The following treatments can be used:
   1. Venesection therapy: Generally, 5–10 ml/kg of blood is removed each time, repeated every 3–5 days, until the HCT reaches < 50%,RBC < 6×10¹²/L. Low-molecular-weight dextran can be administered after venesection to prevent thrombosis.
   2. Chemotherapy: Suitable for patients with excessively high platelet counts (exceeding 800×10⁹/L), those whose symptoms do not improve with frequent venesection, those with significant splenomegaly or hepatomegaly, or those with excessively high levels of uric acid in blood or urine. Commonly used drugs include cyclophosphamide, busulfan, chlorambucil, fortune plumyew twig and leaf alkaloids, etc.
   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 administered once. Generally, 1–2 treatments can achieve remission, but attention should be paid to the bone marrow suppression side effect.