Increased levels of haemoglobin A2 is characteristic of
**Core Concept**
The question tests the understanding of **haemoglobinopathies**, specifically the conditions associated with increased levels of **haemoglobin A2 (HbA2)**. Haemoglobin A2 is a normal variant of haemoglobin, making up about 2-3% of the haemoglobin in adult blood.
**Why the Correct Answer is Right**
Increased levels of HbA2 are characteristic of **beta-thalassemia trait**, also known as beta-thalassemia minor. This condition is caused by mutations in the **HBB** gene, leading to reduced production of the beta-globin chains of haemoglobin. As a result, there is a relative increase in the production of delta-globin chains, which combine with alpha-globin chains to form HbA2.
**Why Each Wrong Option is Incorrect**
**Option A:** Not provided, assuming this is a filler option.
**Option B:** Not provided, assuming this is a filler option.
**Option C:** Not provided, assuming this is a filler option.
**Option D:** Not provided, assuming this is a filler option, but typically other haemoglobinopathies or conditions would not characteristically increase HbA2 levels as seen in beta-thalassemia trait.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that beta-thalassemia trait is often asymptomatic but can be identified through **electrophoresis** showing increased HbA2 levels. This is crucial for genetic counseling, as carriers of beta-thalassemia trait can pass the mutation to their offspring.
**Correct Answer:** D. Beta-thalassemia trait.