MLS Hematology: Thalassemia Patterns, Genetics & Lab Diagnosis

lesson 2

What is thalassemia characterized by?

Reduced globin synthesis.

What are the laboratory goals for thalassemias?

Explain chain imbalance causes anemia and compare common beta and alpha thalassemia patterns.

What is the gene organization for alpha globin?

4 functional genes on chromosome 16 (αα/αα).

What is the gene organization for beta globin?

2 functional genes on chromosome 11 (β/β).

What causes anemia in beta thalassemia?

Reduced β-chain synthesis leading to excess unpaired α chains.

What is the consequence of chain imbalance in thalassemias?

Reduced hemoglobin production and unmatched chains contribute to anemia.

What is ineffective erythropoiesis?

Death of erythroid precursors before useful RBC release.

How does iron loading occur in thalassemia?

Through transfusions and increased intestinal absorption due to ineffective erythropoiesis.

What is the difference between beta zero and beta plus thalassemia?

β⁰ has no β chains from the allele, while β⁺ has reduced β-chain production.

What is the clinical spectrum of beta thalassemia?

Includes transfusion-dependent (TDT) and non-transfusion-dependent (NTDT) forms.

What are the blood film characteristics of beta thalassemia trait?

Microcytosis, hypochromia, target cells, and variable poikilocytosis.

What is Hb Bart?

A tetramer of γ chains (γ₄) associated with alpha thalassemia.

What is HbH?

A tetramer of β chains (β₄) that occurs in alpha thalassemia.

What does the presence of persistent fetal hemoglobin indicate?

More γ-chain production and improved chain balance.

What is the inheritance pattern of beta thalassemia?

Each parent can pass β or β⁰ alleles, leading to various combinations.

What are the typical hemoglobin fractions in untreated beta thalassemia?

Increased HbA₂ and some HbF.

What is the significance of microcytosis in thalassemia?

It can overlap with iron deficiency and indicates a potential thalassemia diagnosis.

What does a CBC pattern in beta thalassemia trait typically show?

Marked microcytosis with a preserved RBC count.

What is the role of chelation therapy in thalassemia?

To remove excess iron from the body.

What is the major treatment goal for patients with thalassemia?

Support oxygen delivery and control iron burden.

What are the potential curative options for thalassemia?

Transplantation and gene therapy.

What does the term 'microcytosis' refer to?

A condition characterized by smaller than normal red blood cells.

What is the effect of HbE on beta thalassemia?

HbE changes the beta-chain structure and reduces effective beta-chain synthesis.

What is the significance of Howell-Jolly bodies in blood films?

They indicate splenic dysfunction or absence.

What is the inheritance risk for two cis carriers of alpha thalassemia?

25% risk of offspring being --/--.

What is the impact of nondeletional alpha thalassemia?

A gene can be present but produce too little functional α globin.

What does the term 'basophilic stippling' indicate?

It can occur in thalassemia and indicates abnormal red blood cell production.

What is the role of molecular testing in thalassemia diagnosis?

To clarify uncertain patterns of hemoglobin production.