A p l a s t i c A n e m i a
Etiology
Acquired
1. Chemical agents
A. Agents with predictable, dose-related effects
• Benzene (a solvent still frequently used in manufacturing)
• radiation (x-rays or other exposures)
• chemotherapeutic drugs
• other toxic substances, such as arsenic
B. Agents with unpredictable, non-dose-related effects
• antimicrobial drugs (e.g., chloramphenicol)
• anticonvulsant drugs
• drugs used in treatment of hyperthyroidism
• insecticides
2. Other causes
• viral infection (e.g., EBV, hepatitis, HIV)
• pregnancy
3. Idiopathic
Familial
Fanconi's anemia (characterized by skeletal abnormalities, chromosomal instability, pancytopenia and increased risk of leukemia) is the most common familial cause.
Clinical features
Incidence
• Rare! Death rate = 1-13 people/1,000,000 per year.
• Not age- or sex-related.
Signs/symptoms are related to cytopenias.
• pallor, dizziness, fatigue (anemia)
• recurrent infection (leukopenia)
• bleeding, bruising (thrombocytopenia)
Morphology
Blood
• Pancytopenia.
• No distinctive red cell abnormalities (anemia is normochromic, normocytic
with minimal anisopoikilocytosis).
Bone marrow
• Markedly hypocellular.
• Bone marrow aspirate specimen consists mostly of lymphocytes!
Differential diagnosis (given only blood findings)
• Disorders infiltrating the bone marrow (e.g., "aleukemic" leukemia,
myelofibrosis, metastatic carcinoma).
• Disorders involving the spleen (e.g., congestive splenomegaly, lymphoma).
• Miscellaneous disorders (e.g., overwhelming infection, refractory anemia).
Treatment and prognosis
• Avoid further exposure, if anemia is result of known noxious agent.
• Transfuse specific blood components as needed (red blood cells, platelets).
• Drug therapy: stimulate hematopoiesis (G-CSF, steroids, androgens) and
suppress immune system (anti-thymocyte globulin or ATG).
• Bone marrow transplant if above approaches fail.
• Prognosis (with treatment): 3-year survival = 70%.
