Thrombocytosis can be classified into primary and secondary types. Primary or essential thrombocythemia is a type of myeloproliferative disorder, predominantly affecting adults and rarely seen in children, with about 5% of pediatric cases potentially progressing to acute leukemia. Secondary or reactive thrombocytosis may occur in:

1. Inflammatory diseases: such as various bacterial and viral infections, Bi disease, rheumatoid Bi disease, Kawasaki disease, ulcerative colitis, regional enteritis, subcutaneous nodule disease, fleshy tumor-like conditions, hepatitis, osteomyelitis, thrombophlebitis, etc.
2. Hematologic diseases and tumors: including hemorrhage, chronic hemolytic anemia, hemoglobinopathies, megaloblastic anemia, lymphoma, neuroblastoma, Langerhans cell histiocytosis, carcinoma, etc.
3. Others: such as postoperative states, post-splenectomy, adrenal cortical hyperfunction, trisomy 21 syndrome, etc.

bubble_chart Diagnosis

(1) Secondary Thrombocytosis

1. Clinical Manifestations

1. There are clinical manifestations of the primary disease or identifiable predisposing factors.
2. Marked thrombocytosis may lead to thrombosis or bleeding tendencies, which are generally mild.
3. After removing the disease cause, platelet counts can gradually return to normal, and the course is brief.

1. Platelet count ≥400×10⁹/L, generally <800 ×10⁹/L, with normal platelet morphology and generally normal function.
2. Bone marrow shows increased megakaryocytes with reduced size.

1. Clinical Manifestations

1. About 1/5 of patients may experience bleeding of varying degrees and locations, with skin and mucous membrane bleeding being most common, and occasionally hematemesis, hematochezia, or muscle and joint bleeding.
2. Manifestations of thrombosis in different locations may occur.
3. Splenomegaly is common (>80% of cases).

1. Platelet count >1000×10⁹/L (international standard >600×10⁹/L). Blood smears may show platelet clumps, giant platelets, and increased white blood cell and neutrophil counts.
2. Bone marrow is hypercellular with increased megakaryocytes (mostly mature type), enlarged size, and abundant cytoplasm.
3. Platelet aggregation responses to epinephrine and collagen may be reduced. Adhesion and release reactions are weakened, and platelet factor 3 (PF3) activity is decreased.

bubble_chart Treatment Measures

(1) For secondary cases, the primary focus is on treating the underlying disease. In severe cases, medications such as aspirin and dipyridamole may be tried to prevent thrombosis.

(2) For primary cases, drugs that suppress bone marrow proliferation may be used, such as:

1. **Radioactive phosphorus (32P):** The initial dose is 3–4 millicuries (adjusted for children), administered orally or intravenously. Platelet counts typically decrease 3 weeks after administration. If necessary, a repeat dose may be given after 3 months.
2. **Chemotherapy:** Busulfan may be used at 4–8 mg/day, divided into two oral doses. The dose is reduced once the platelet count decreases by 50% and gradually tapered or discontinued as levels approach normal. Other options include hydroxyurea, cyclophosphamide, fortune plumyew twig and leaf alkaloids, etc. The domestic drug meisoindigo is also effective. Interferon may be used for maintenance therapy.
3. **Anticoagulants:** To prevent thrombosis, aspirin, dipyridamole, indomethacin, or dextran may be used. Heparin or ethyl biscoumacetate can also be employed for anticoagulation.