Inherited disorders in which a genetic defect causes abnormalities in rate and quantity of synthesis of structurally normal polypeptide chains of the hemoglobin molecule are called?

• A. Thalassemias
• B. Hemoglobinopathies
• C. Porphyrias
• D. Molecular dyscrasias

Answer: (A)

Thalassemias are inherited conditions where a genetic defect lowers the production rate of one or more globin polypeptide chains, so the chains that are made are structurally normal but are produced in insufficient quantities. This imbalance in globin synthesis leads to anemia and related findings because there isn’t enough normal hemoglobin to meet the body's needs. The key point is that the problem lies in how much of the chains are produced, not in a change to their structure.

In contrast, disorders called hemoglobinopathies involve abnormal structure of the globin chains or hemoglobin molecules themselves, such as structural mutations that change the amino acid sequence. Porphyrias are disorders of heme biosynthesis, not of globin production. Molecular dyscrasias is an imprecise term and does not specifically describe reduced globin synthesis with structurally normal chains.