单细胞系再障：APLASIAS OF SINGLE CELL LINEAGES（英语学习）
In contrast to aplastic anemia (再生障碍性贫血), in which all three cell lines are affected, patients sometimes have aplasia restricted to a single cell lineage (单细胞谱系). Such patients lack both the marrow precursors (前体细胞) and the mature circulating cells of the affected lineage, a situation different from those syndromes such as hemolytic anemia (溶血性贫血) or immune-mediate thrombocytopenia (免疫介导的血小板减少症) in which the problem is one of destruction of the mature blood element rather than its production.
Aplastic anemia is defined by the presence of pancytopenia (全血细胞减少症) in the peripheral blood (外周血) and a bone marrow that is markedly hypocellular and largely replaced by fat. Although a similar condition regularly occurs in patients receiving chemotherapy (化疗) or radiotherapy (放疗) for malignant disease, such patients quickly recover and are not considered to have Aplastic anemia. Aplastic anemia may be categorized as mild or severe. Severe Aplastic anemia has been defined by the International Aplastic Anemia Study Group as follows: (1) a marrow of less than 25% marrow cellularity and (2) at least two of the following three peripheral blood values: neutrophil granulocytes less than 0.5×109 per liter, platelets less than 20×109 per liter, and anemia with reticulocytes less than 1% (corrected for the hematocrit). Within this group, those with extreme neutropenia (<0.2×109 per liter) have the worst outlook. Mild aplastic anemia is defined as marrow hypoplasia (骨髓增生减低) with cytopenias (血细胞减少症) in two or more cell lines, but not severe enough to meet (满足) the preceding criteria.
Pure Red Blood Cell Aplasia （PRCA，纯红细胞再障，纯红再障）
Pure red blood cell aplasia (PRCA) occurs as a congenital (先天的) or an acquired (后天的) syndrome. The congenital form, Diamond-Blackfan syndrome (戴-布二氏综合征，先天性纯红再障), usually becomes evident as an isolated anemia during the first 2 years of live. The disease is thought to be transmitted as an autosomal recessive trait (常染色体隐性遗传特质) and in 25% of cases is associated with other minor congenital anomalies. The disorder responds to glucocorticoids in 50% to 75% of cases, and occasionally patients who fail glucocorticoid therapy respond to other immunosuppressants (免疫抑制剂). Marrow transplantation (骨髓移植) has been used in corticosteroid-resistant patients and can cure the disease.
Primary acquired PRCA has both acute and chronic forms. The acute form of PRCA is most often seen in young patients with underlying hemoglobinopathy (血红蛋白病) or hemolytic anemia. The disease often follows a relatively mild viral infection, most often with parvovirus (微小病毒). The disease is usually self-limited; therefore the appropriate management involves maintaining an adequate hemoglobin level with red blood cell transfusions during the period of severe anemia and administration of folic acid 1mg/day during the regenerative phase to prevent folate deficiency. The chronic form of PRCA is usually seen in patients aged 20 to 50 years, becoming evident as a slowly progressive anemia. Thymomas (胸腺瘤) are sometimes found in cases of PRCA. While the exact incidence of thymoma in PRCA is unknown, most studies put the incidence at 15 to 20%. Most often these tumors are of the spindle cell type and behave as benign tumors. PRCA is sometimes associated with other diseases such as chronic lymphocytic leukemia or systemic lupus erythematosus (SLE，系统性红斑狼疮) and rarely occurs with the same groups of drugs associated with aplastic anemia. In many patients complement-fixing immunoglobulin G (IgG) selectively cytotoxic to marrow erythroblasts (幼红细胞) can be detected and is thought to be causative. Management of patients with PRCA begins with discontinuation of any suspected offending agent followed by a search for a thymoma. Thymectomy induces remission in 50% of patients with an enlarged thymus but is not effective in those with normal-sized thymuses (胸腺). For patients without thymoma or for whom thymectomy fails, a trial of immunosuppressive therapy is warranted. Glucocorticoid or cyclosporine is usually the first agent of choice; ATG and cytotoxic immunosuppressants such as cyclophosphamide (CTX，环磷酰胺) and azathioprine (硫唑嘌呤) are reserved for treatment failures.
Pure White Blood Cell Aplasia (纯白细胞再障)
Pure white blood cell aplasia is a very rare condition with parallels to PRCA in that it appears to have an immune basis and is sometimes associated with thymoma, whereas in other cases it appears to be drug-related. Management, like that of PRCA, involves removal of any identified offending agent, thymectomy if an enlarged thymus is found, and immunosuppressive therapy with glucocorticoids or cyclosporine for patients in whom the first two maneuvers are inappropriate or unsuccessful.
Pure Amegakaryocytic Thrombocytopenic Purpura (PATP，纯无巨核细胞性血小板减少性紫癜)
Pure amegakaryocytic thrombocytopenic purpura (PATP) is a rare syndrome characterized by severe thrombocytopenia associated with a total absence or a marked reduction of bone marrow megakaryocytes. Changes in other cell lines are minimal or absent. PATP has been attributed to viral infections, toxin or drug exposure, or immune-mediated suppression of megakaryocytopoiesis (巨核细胞生成). Patients generally have symptoms caused by cutaneous or mucous membrane hemorrhage (出血). Physical examination findings are otherwise normal. Laboratory evaluation findings reveal severe thrombocytopenia with normal or small platelets, as opposed to the large platelets of idiopathic thrombocytopenic purpura (ITP，特发性血小板减少性紫癜), and bone marrow that is normal except for the virtual absence of identifiable (可确认的) megakaryocytes (巨核细胞). Therapy is directed at removal of all possible offending agents and administration of platelet transfusion support. Responses to other therapies, such as those using corticosteroids, gamma-globulin infusions, cyclosporine, and cyclophosphamide, are largely anecdotal (无对照的，亦即根据无对照的个案病例描述的而不是根据对照研究的).