Aplastic anemia overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Priyamvada Singh, M.D. [2] Nazia Fuad M.D.
Overview
Anemia is the condition of having fewer red blood cells than normal, or fewer than needed to function properly. Typically, anemia refers to low red blood cell counts, but aplastic anemia patients have lower counts of all three blood cell types: red blood cells, white blood cells, and platelets. Bone marrow is a sponge-like tissue inside the bones. It makes stem cells that develop into red blood cells, white blood cells, and platelets. Aplastic anemia is a condition where bone marrow does not produce sufficient new cells to replenish blood cells. The term 'aplastic' means the marrow suffers from an aplasia that renders it unable to function properly. Red blood cells carry oxygen to all parts of your body. They also carry carbon dioxide (a waste product) to your lungs to be exhaled. White blood cells help your body fight infections. Platelets are blood cell fragments that stick together to seal small cuts or breaks on blood vessel walls and stop bleeding. It's normal for blood cells to die. The lifespan of red blood cells is about 120 days. White blood cells live less than a day. Platelets live about 6 days. As a result, the bone marrow must constantly make new blood cells. If the bone marrow can't make enough new blood cells, many health problems can occur. These problems include arrhythmias, an enlarged heart, heart failure, infections, and bleeding. Severe aplastic anemia can even cause death.
Historical Perspective
Paul Ehrlich in 1988 made known the notion of aplastic anemia. He narrated the case of a pregnant lady, who died of bone marrow failure. In1904 Anatole Chauffard named this disorder aplastic anemia. In 1920s and 1930s Alice Hamilton and Harrison recognised bone marrow failure in workers who were exposed to benzene in the United States. In the late 1940s and early 1950s, an epidemic of aplastic anemia started showing up in people who were recieving chloramphenicol, and then aplastic anemia has been related to many classes of drugs generally used in medical practice. Neal Young from john hopkins in 1980s introduced an immunosuppressive regimen which proved to be very effective treatment for aplastic anemia.
Classification
Aplastic anemia may be classified according to blood cell counts into 3 subgroups, moderately severe aplastic anemia or non severe AA (nSAA), severe aplastic anemia (SAA), and very severe aplastic anemia(vSAA)
Pathophysiology
Bone marrow is a spongy tissue, found within the spongy or cancellous portions of bones. It is higly vascularized and richly innervated Bone marrow is the primary site of hematopoiesis and is composed of hematopoietic cells, marrow adipose tissue, and stromal cells. The most defenitive feature in pathophysiology of aplastic anemia is loss of hematopoietic stem cells. It may be in the form of hematopoietic failure or immune mediated destruction of bonemarrow. Drugs, chemicals, viruses, and different kind of mutations change the immunologic appearance of HSCs resulting in autoimmune destruction of marrow cells. AA may develop gradually into other hematologic disorder which include paroxysmal nocturnal hemoglobinuria [PNH], myelodysplastic syndromes [MDS] and acute myeloid leukemia [AML]). Clonal evolution in AA can occur due to mutations or cytogenetic abnormalities. The genes that are commonly found to be mutated are DMNT3A, ASXL1, BCOR, BCORL1, PIGA.
Causes
Common causes of aplastic anemia include hepatitis, Epstein-Barr virus, cytomegalovirus, parvovirus B19, and HIV. Medicines, such as Albendazole, Cefadroxil, Chlorpromazine, chloramphenicol , Carbamazepine, Hydroxychloroquine, Methimazole, Orphenadrine, Oxcarbazepine, Phenytoin, Quinine, Phenylbutazone, Sulindac, Sulfadiazine, Sulfasalazine, Valganciclovir hydrochloride. Other causes include radiation, chemotherapy, toxins, such as pesticides, arsenic, and benzene, and metastasis to bone marrow. Less common causes of aplastic anemia are Lupus (SLE), rheumatoid arthritis, .pregnancy, Thymoma, and collagen vascular disease.
Differentiating [disease name] from other Diseases
- [Disease name] must be differentiated from other diseases that cause [clinical feature 1], [clinical feature 2], and [clinical feature 3], such as:
- [Differential dx1]
- [Differential dx2]
- [Differential dx3]
Epidemiology and Demographics
- The prevalence of [disease name] is approximately [number or range] per 100,000 individuals worldwide.
- In [year], the incidence of [disease name] was estimated to be [number or range] cases per 100,000 individuals in [location].
Age
- Patients of all age groups may develop [disease name].
- [Disease name] is more commonly observed among patients aged [age range] years old.
- [Disease name] is more commonly observed among [elderly patients/young patients/children].
Gender
- [Disease name] affects men and women equally.
- [Gender 1] are more commonly affected with [disease name] than [gender 2].
- The [gender 1] to [Gender 2] ratio is approximately [number > 1] to 1.
Race
- There is no racial predilection for [disease name].
- [Disease name] usually affects individuals of the [race 1] race.
- [Race 2] individuals are less likely to develop [disease name].
Risk Factors
Aplastic anemia is a rare but serious blood disorder. Common risk factors in the develpment of aplastic anemia are radiation treatment, drugs and toxin exposure, chemotherapy, PNH, and viral hepatitis. Less common risk factors are pregnancy, benzene, pesticides, rheumatoid arthritis and SLE.
Natural History, Complications and Prognosis
Aplastic anaemia has a mixed clinical course. Untreated aplastic anemia leads to rapid death, typically within six months. Complications following development of aplastic anemia are infections, bleeding and paroxysmal nocturnal hemoglobinuria. Graft-versus-host disease and graft failure are the possible complications following bone marrow transplant in these patients. Mild cases resolve on their own requiring little or no treatment. Well-matched bone marrow transplants from siblings have been successful in young individuals with a long-term survival rate of 80%-90%
Diagnosis
Diagnostic Criteria
- The diagnosis of [disease name] is made when at least [number] of the following [number] diagnostic criteria are met:
- [criterion 1]
- [criterion 2]
- [criterion 3]
- [criterion 4]
Symptoms
- [Disease name] is usually asymptomatic.
- Symptoms of [disease name] may include the following:
- [symptom 1]
- [symptom 2]
- [symptom 3]
- [symptom 4]
- [symptom 5]
- [symptom 6]
Physical Examination
- Patients with [disease name] usually appear [general appearance].
- Physical examination may be remarkable for:
- [finding 1]
- [finding 2]
- [finding 3]
- [finding 4]
- [finding 5]
- [finding 6]
Laboratory Findings
- There are no specific laboratory findings associated with [disease name].
- A [positive/negative] [test name] is diagnostic of [disease name].
- An [elevated/reduced] concentration of [serum/blood/urinary/CSF/other] [lab test] is diagnostic of [disease name].
- Other laboratory findings consistent with the diagnosis of [disease name] include [abnormal test 1], [abnormal test 2], and [abnormal test 3].
Imaging Findings
- There are no [imaging study] findings associated with [disease name].
- [Imaging study 1] is the imaging modality of choice for [disease name].
- On [imaging study 1], [disease name] is characterized by [finding 1], [finding 2], and [finding 3].
- [Imaging study 2] may demonstrate [finding 1], [finding 2], and [finding 3].
Other Diagnostic Studies
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- Findings on [diagnostic study name] include [finding 1], [finding 2], and [finding 3].
Treatment
Medical Therapy
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- The mainstay of therapy for [disease name] is [medical therapy 1] and [medical therapy 2].
- [Medical therapy 1] acts by [mechanism of action 1].
- Response to [medical therapy 1] can be monitored with [test/physical finding/imaging] every [frequency/duration].
Surgery
- Surgery is the mainstay of therapy for [disease name].
- [Surgical procedure] in conjunction with [chemotherapy/radiation] is the most common approach to the treatment of [disease name].
- [Surgical procedure] can only be performed for patients with [disease stage] [disease name].
Prevention
- There are no primary preventive measures available for [disease name].
- Effective measures for the primary prevention of [disease name] include [measure1], [measure2], and [measure3].
- Once diagnosed and successfully treated, patients with [disease name] are followed-up every [duration]. Follow-up testing includes [test 1], [test 2], and [test 3].