beta thalassemia
b-thalassemia
Updated: 07/12/2024
© Jun Wang, MD, PhD
General features
- Very heterogenous etiology
- Autosomal recessive, usually point mutations,
- Reduced synthesis of beta globin chains (2 genes)
- Two categories
o B0: absent b-globin synthesis
o B+: reduced b-globin synthesis
- May also be classified by clinical severity
o Minor: Hb >10 gm/dL, normal to slightly elevated HbA2, HbF
o
Intermedia: Hb of
7.0-10 gm/dL, slightly elevated Hb2A, 20-40% HbF
o Major: Hb < 7.0 gm/dL, no or minimal HbA, predominately HbF
- Diagnosed by clinical features, Hb studies
Pathogenesis
- Decreased Hgb production
- Excess unpaired a chains precipitate out in erythroids
o Ineffective erythropoeisis
o Membrane damage
- Extravascular hemolysis: RBCs with inclusions and membrane damage removed from the circulation
- Enlargement of liver and spleen due to:
o Red cell destruction
o Extramedullary hematopoiesis
o Iron overload later in the course of disease
Clinical features
- Failure to thrive, pallor and abdominal swelling
- Enlargement of liver and spleen
- Facial feature due to bone expansion by marrow hyperplasia
- “Chipmunk facies” with frontal bossing, maxillary expansion, saddle nose and depressed cranial vault
- “Crew-cut/hair on end appearance”: vertical striations due to extramedullary haematopoiesis
- Osteoporosis due to endocrine disorders, iron toxicity, and erythroid proliferation
- Risk of infections due to anemia, iron overload, splenectomy
Laboratory findings
- Severe anemia at 6 – 9 months as HbF decreases
- Microcytic (M), hypochromia, anisocytosis, poikilocytosis, Target cells (T), basophilic stippling, and nucleated RBC
- Increased reticulocytes
Hb electrophoresis findings
- High HbF, low HbA
Management
- No specific treatment for beta thal minor
- Treatment for beta thal major
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