A 3-year-old child with β-thalassemia major on regular transfusions presents with bone pain and facial deformity. Which histopathologic finding in the bone marrow best distinguishes the skeletal changes of thalassemia from those of hereditary spherocytosis?
A. Fibrosis and aplasia of hematopoietic tissue
B. Deposition of hemosiderin in osteocytes and osteoblasts
C. Osteoclast activation and increased bone resorption
D. Massive erythroid hyperplasia with expansion of red marrow into long bones
Explanation
Skeletal Pathology in Thalassemia vs. Hereditary Spherocytosis
Key Point
Massive erythroid hyperplasia with expansion of red marrow into long bones is the distinguishing feature of thalassemia's skeletal involvement. Hereditary spherocytosis does not cause this degree of marrow expansion.
Pathophysiology of Skeletal Changes in Thalassemia
Thalassemia:
1.
Severe chronic hemolysis and ineffective erythropoiesis → intense compensatory erythroid hyperplasia.
2.
Erythroid progenitors expand dramatically in the bone marrow.
3.
Red (hematopoietic) marrow replaces yellow (fatty) marrow throughout the skeleton, including long bones (femur, tibia, humerus).
Vertebral bodies become osteoporotic and may collapse.
Hereditary Spherocytosis:
Chronic hemolysis is present, but less severe than in thalassemia major.
Erythroid hyperplasia occurs but is modest.
Marrow expansion is minimal and does not extend into long bones.
Skeletal deformities are rare and mild.
Patients do not develop the characteristic facial deformities or severe osteoporosis seen in thalassemia.
Comparison of Skeletal Features
Table
Feature
β-Thalassemia Major
Hereditary Spherocytosis
Marrow hyperplasia
Massive, extends to long bones
Mild, confined to axial skeleton
Red marrow expansion
Replaces yellow marrow throughout
Minimal expansion
Facial deformity
Severe (frontal bossing, maxillary prominence)
Absent or minimal
Cortical thinning
Marked
Absent
Pathologic fractures
Common
Rare
Vertebral collapse
Common
Rare
Osteoporosis severity
Severe
Mild
High-YieldNEET PG
The extent and distribution of marrow hyperplasia is the key histopathologic discriminator. Thalassemia causes marrow expansion into normally fatty long bones; hereditary spherocytosis does not.
Clinical Pearl
A child with thalassemia major presenting with facial deformity, bone pain, and pathologic fractures reflects the skeletal consequences of massive, unrelenting marrow hyperplasia. Hereditary spherocytosis, despite chronic hemolysis, rarely causes such severe skeletal involvement because the hemolysis is less severe and the marrow response is proportionally less dramatic.
Why Hemosiderin Deposition Is Not the Discriminator
While iron overload (from transfusions and hemolysis) does occur in thalassemia and can deposit in bone cells, hemosiderin deposition is a consequence of transfusion and hemolysis, not the primary cause of skeletal deformity. The skeletal changes are driven by the marrow hyperplasia itself.
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