1.1 Etiology

1.1 Etiology

The etiology of aplastic anemia is not yet fully understood. Known factors include damage to multipotent bone marrow stem cells and the microenvironment, leading to a series of functional and morphological changes, which further result in a common hematological disease characterized by a reduction in all blood cells. The currently widely accepted pathogenesis is defects in hematopoietic stem cells, immune abnormalities, and disturbances in the hematopoietic microenvironment [8]. Most scholars recognize that autoimmunity plays a role in the development of most cases of aplasia, and the immune pathogenesis of aplasia has also attracted the attention of TCM researchers. As TCM research on aplasia deepens both clinically and experimentally, exploring the immune regulatory mechanisms of TCM treatment for aplasia has gradually become a research hotspot. After more than 40 years of combined TCM and Western medicine treatment, the prognosis has improved to a certain extent. According to surveys, the average survival period has been extended, and the mortality rate has decreased. Acute aplasia is often triggered by immune abnormalities, leading to rapid destruction and suppression of a large number of hematopoietic cells and bone marrow stromal cells—this is known as immune-mediated aplasia.

1.1.1 Chemical Factors

Chemical substances such as benzene and its derivatives, organic phosphorus pesticides are common, and drugs that often cause this disease include chloramphenicol, polymyxin, antipyretic analgesics, sulfonamides, tetracyclines, anti-tumor drugs, insecticides, anti-tuberculosis drugs (such as isoniazid), and anti-thyroid drugs (such as methimazole and methylthiouracil) [9]. Among these chemicals, some have a dose-dependent inhibitory effect on bone marrow (such as benzene and its derivatives, anti-tumor drugs), while others (such as antibiotics, insecticides, sulfonamides) cause aplasia regardless of dosage, depending instead on individual sensitivity, often with more severe consequences.

1.1.2 Physical Factors

Mainly various ionizing radiations, such as X-rays, radioactive isotopes, gamma rays, etc., which can inhibit cell mitosis by interfering with DNA replication, thereby reducing the number of hematopoietic stem cells and disrupting bone marrow cell production. According to statistics, individuals who receive radiation therapy or undergo diagnostic imaging too frequently have a 10-fold higher risk of developing aplasia compared to the control group [10].

1.1.3 Biological Factors

Viruses are closely related to the onset of aplasia. The most common is hepatitis virus. The mechanism by which hepatitis causes aplasia is that the virus directly damages bone marrow hematopoietic stem cells. From an embryological perspective, the liver and bone marrow both belong to the mononuclear-macrophage system, so this inhibitory factor may have cross-effects on the liver and bone marrow. In addition, various severe infections can also affect bone marrow hematopoiesis.