Aplastic Anemia
INTRODUCTION:
- Pancytopenia resulting from aplasia of bone marrow.
- Bone marrow produces very few blood cells includes red cells, white cells, and platelets (pancytopenia).
- Is a syndrome of chronic primary hemopoeitic failure.
- Classified into primary & secondary types.
ETIOLOGY:
Primary:
- Congenital
- Eg: Fanconi’s anemia – Autosomal recessive inheritance with defects in tolemerase activity.
Idiopathic acquired (67% of cases) due to,
- Primary defect in number or function of stem cells.
- Mutagen exposure.
- Genetically damaged stem cells transferred to myeloid neoplasms.
- Supppression of antigenically altered stem cells T-cell mediated immune mechanisms.
Secondary:
- Chemicals (benzene, toluene, glue sniffing).
- Dose-related, predictable & reversible.
Drugs
- Chemotherapeutics, antibiotics, gold, carbamazepine, phenytoin, Chloramphenicol, vincristine, chlropromazine, streptomycin.
- Insecticides.
- Ionizing radiation (Total body irradiation).
- Infections (as non-A, non-B, non-C, & non-G hepatitis).
- Parvovirus
- HIV-1
- Pregnancy
- Drugs like .
- Paraxysmal nocturnal haemoglobinuria.
PATHOGENESIS:
- Reduction in number of haemopoietic pluripotential stem cells due to faulty stem cells.
- Immune reaction against stem cell : Inability to divide & differentiate sufficiently to produce blood cells.
CLINICAL FEATURES:
- Occurs at any age.
- Male predominance.
- Anemia with associated symptoms like malaise, pallor, & palpitations.
- Fever
- Weakness
- Thrombocytopenia (low platelet counts), leading to increased risk of hemorrhage, bruising and petechiae.
- Leukopenia (low white blood cell count), particularly grnaulocytopenia, leading to increased risk of infection.
- Reticulocytopenia (lower reticulocyte counts).
- Splenomegaly is absent.
DIAGNOSIS:
Complete Blood Picture (CBP):
- Shows pancytopenia & reticulocytes.
- The image on left side shows aplastic marrow & right shows normal bone marrow.
Bone marrow aspirate:
- Bone marrow aspirate usually yield “Dry tap”.
- A trephine biopsy essential for diagnosis.
- Revelas markedly hypocellular marrow with patchy cellular areas due to replacement of hemopoietic marrow by adipose tissue (not fibrosis or neoplastic cells).
THERAPY:
General:
- Removal of cause.
- Supportive care with blood transfusion – Platelet concentrate.
- Prevention of infection.
Specific:
BONE MARROW TRANSPLANTATION:
- Treatment of choice.
- From HLA matched donor (Usually siblings).
- Long term survival rates: 60-70%.
- IMMUNOSUPPRESSION: By using drugs
- Marrow stimulation agents
- Splenectomy
Exam Question
- A patient aged 65 years, is diagnosed to have severe aplastic anemia with HLA compatible sibling is best treated with Antithymocyte globulin followed by cyclosporine
- Carbamazepine may lead to aplastic anemia.
- Parvovirus causes aplastic anemia in chronic hemolytic diseases
- Pancytopenia is caused by Aplastic anemia
- Reticulocytopenia is caused by Aplastic anemia
- Aplastic anemia can progress to AML,Myelodysplastic anemia,Paroxysmal nocturnal hemoglobinuria
- Splenectomy done in Aplastic anemia.
- Aplastic anemia is seen in PNH,Chloramphenicol,HIV- I, Pregnancy (rare), Gold salts.
- Fever, weakness, splenomegaly, low hemoglobin & pancytopenia are features seen in aplastic anemia.
- Most common cause of aplastic anemia is Exposure to drugs.
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