Hypoplastic and Aplastic Anemia
(Etiology, Pathogenesis, and Clinical Manifestations)
Hypoplastic anemia: A condition where the bone marrow shows reduced cellularity, leading to decreased blood cell production (especially red cells).
Aplastic anemia: A severe form of hypoplastic anemia in which the bone marrow fails to produce all three cell lines (RBCs, WBCs, platelets) → pancytopenia.
Etiology
Congenital causes:
Fanconi anemia – inherited DNA repair defect.
Dyskeratosis congenita.
Acquired causes:
- Idiopathic (~50% of cases).
- Drugs:
- Chemotherapy, chloramphenicol, NSAIDs, antiepileptics.
- Toxins:
- Benzene, radiation.
- Infections:
- Parvovirus B19, EBV, HIV, hepatitis viruses.
- Autoimmune:
- T-cell–mediated suppression of hematopoiesis.
Pathogenesis
- Injury to hematopoietic stem cells (by drugs, viruses, autoimmune attack, etc.).
- Decreased proliferation of myeloid, erythroid, and megakaryocytic lineages.
- Bone marrow becomes hypocellular with fatty replacement.
- Leads to pancytopenia → anemia, leukopenia, and thrombocytopenia.
Clinical Manifestations
Due to anemia (↓ RBCs):
Fatigue, weakness.
Pallor.
Dyspnea on exertion.
Due to leukopenia (↓ WBCs):
Frequent infections.
Fever, oral ulcers.
Due to thrombocytopenia (↓ platelets):
Easy bruising.
Petechiae, purpura.
Nosebleeds, gum bleeding.
Diagnosis clues
CBC: Pancytopenia.
Reticulocyte count: ↓ ↓ (low production).
Bone marrow biopsy: Hypocellular marrow with fat spaces.
Rule out leukemia, myelodysplasia.