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. 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.
Causes
One known cause is an autoimmune disorder, where the white blood cells attack the bone marrow.
In many cases, the etiology is impossible to determine, but aplastic anemia is sometimes
associated with exposure to substances such as benzene, radiation, or to the use of certain drugs, including chloramphenicol,
carbamazepine, phenytoin, quinine, and phenylbutazone. Many drugs are associated with aplasia
mainly in the base of case reports but at a very low probability, As an example, chloramphenicol treatment is followed by aplasia
in less than 1 in 40,000 treatment courses,and carbamazepine aplasia is even more rare.
Aplastic anaemia is present in up to 2% of patients with acute viral hepatitis.
Signs and symptoms
Diagnosis
The diagnosis can only be made on bone marrow examination. Before this
procedure is undertaken, a patient will generally have had other blood tests to find
diagnostic clues, including a full blood count, renal function and electrolytes, liver enzymes, thyroid function tests, vitamin B12 and folic acid levels.
Treatment
Treating aplastic anemia involves suppression of the immune system, an effect achieved
by daily medicine intake, or, in more severe cases, a bone marrow transplant, a potential cure but a risky procedure. The transplanted
bone marrow replaces the failing bone marrow cells with new ones from a matching donor. The pluripotent stem cells in the bone marrow reconstitute all three blood cell lines, giving the patient a new
immune system, red blood cells, and platelets. However, besides the risk of graft failure, there is also a risk that the newly
created white blood cells may attack the rest of the body ("graft-versus-host
disease").
Medical therapy of aplastic anemia often includes a short course of anti-thymocyte
globulin (ATG or anti-lymphocyte globulin) and several months of
treatment with cyclosporin to modulate the immune
system. Mild chemotherapy with agents such as cyclophosphamide and vincristine may also be effective.
Antibodies therapy, such as ATG, targets T-cells, which are believed to attack the bone marrow.
Steroids are generally ineffective.
In the past, before the above treatments became available, patients with low leukocyte counts were often confined to a sterile
room or bubble (to reduce risk of infections), as in the famed case of Ted DeVita.
Prognosis
Untreated aplastic anemia is an illness that leads to rapid death, typically within six months. If the disease is diagnosed
correctly and initial treatment is begun promptly, then the survival rate for the next five to ten years is substantially
improved, and many patients live well beyond that length of time.[citation needed]
Occasionally, milder cases of the disease resolve on their own. Relapses of previously controlled disease are, however, much
more common.
Well-matched bone marrow transplants from siblings have been successful in young, otherwise healthy people, with a long-term
survival rate of 80%-90%. Most successful BMT recipients eventually reach a point where they consider themselves cured for all
practical purposes, although they need to be compliant with follow-up care permanently.[citation needed]
Older people (who are generally too frail to undergo bone marrow transplants) and people who are unable to find a good bone
marrow match have five year survival rate of up to 75%.
Follow-up
Regular full blood counts are required to determine whether the patient is still
in a state of remission.
10-33% of all patients develop the rare disease paroxysmal nocturnal hemoglobinuria (PNH, anemia with thrombopenia and/or
thrombosis), which has been explained as an escape mechanism by the bone marrow against
destruction by the immune system. Flow cytometry testing is probably warranted in all PNH
patients with recurrent aplasia.
See also
External links
|
Pathology: hematology
(primarily
C81-C96/200-208,
D45-D47, D50-D77/280-289) |
| WBCs |
hematological
malignancy (Lymphoma, leukemia)
-cytosis (Agranulocytosis, Leukocytosis,
Lymphocytosis, Monocytosis) • -penia
(Lymphopenia, Neutropenia) |
RBCs/anemia/
hemoglobinopathy |
nutritional anemia: Iron deficiency anemia, Plummer-Vinson syndrome,
Megaloblastic anemia (Pernicious
anemia)
hereditary hemolytic anemia: G6PD Deficiency, Thalassemia,
Sickle-cell disease/trait,
Hereditary spherocytosis, Hereditary elliptocytosis, Hereditary
stomatocytosis
acquired hemolytic anemia: Warm autoimmune hemolytic anemia,
HUS, MAHA,
PNH
aplastic anemia: Acquired
PRCA, Diamond-Blackfan anemia, Fanconi
anemia • Sideroblastic anemia • Hemochromatosis |
| Coagulation/platelets |
coagulopathy:
DIC • Hemophilia
(A, B, C,
XIII) • Von Willebrand
disease
Purpura: Henoch-Schönlein,
ITP, TTP
primary hypercoagulable state: Protein C deficiency - Protein S deficiency - Antithrombin III
deficiency
other hemorrhagic conditions: Bernard-Soulier syndrome -
Glanzmann's thrombasthenia - Grey
platelet syndrome |
| Histiocytosis |
WHO-I Langerhans cell histiocytosis - non-Langerhans-cell histiocytosis/WHO-II
(Juvenile xanthogranuloma, Hemophagocytic lymphohistiocytosis) - malignant histiocytic disorders/WHO-III
(Acute monocytic leukemia, Malignant
histiocytosis, Erdheim-Chester disease) |
| Other |
Asplenia/hyposplenism -
Methemoglobinemia |
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