A variety of genetic blood disorders are known as thalassemias, all of which are characterized by abnormal hemoglobin production. Hemoglobin is a protein in red blood cells that chiefly functions in the transport of oxygen from the lungs to the tissues of the body.

Thus, many thalassemias are characterized by symptoms resulting from insufficient oxygen. Thalassemias are typically classed as either alpha thalassemias or beta thalassemias depending on whether the hemoglobin abnormality results from aberrant alpha or beta proteins. Beta thalassemias are the most familiar form of the disease and these disorders are further subdivided clinically into three subtypes: thalassemia minor, thalassemia intermedia, and thalassemia major.

Thalassemia minor is the least serious of the forms of beta thalassemia. In fact, the condition is often asymptomatic, though patients with the disease produce red blood cells that are smaller than normal and are, therefore, capable of carrying less oxygen than typical red blood cells. Thalassemia minor is sometimes accompanied by mild anemia and on rare occasions can lead to minor swelling of the spleen. Usually, however, no treatment is necessary.

The autosomal recessive pattern of genetic transmission of beta thalassemia was deduced by the prominent American geneticist James V. Neel. At first, Neel was perplexed by the fact that beta thalassemia occurs with such a high frequency since the homozygous form of the condition, thalassemia major, is very serious and generally leads to premature death. He initially suspected a high rate of mutation. Eventually, however, Neel realized that the heterozygous form of beta thalassemia, as well as the sickle-cell disease that also consumed his early studies, provided individuals with resistance to malaria, thus making its preponderance in the human population understandable. Neel’s reasoning also helps explain why prevalence of beta thalassemia is greatest in people of Mediterranean, Middle Eastern, and south Asian heritage, since these parts of the world were historically beset with malaria.

Thalassemia is also known as Cooley's anemia, Mediterranean anemia, and hereditary leptocytosis. The common medical term for the disease was coined by Nobel laureate George Whipple and William Bradford, a professor of pediatrics, from the Greek word thalassa, meaning “sea” and the suffix -emia, which refers to blood. Their decision was meant to reflect the predominance of the gene for beta thalassemia among Greeks, Italians, and others from areas around the Mediterranean Sea. The disease also occurs in other peoples, however, including Native Americans and northern Europeans, but to a much lesser extent. Studies show that among individuals of African descent beta thalassemia is significantly less serious than usual.

Thalassemia Minor at 20x Magnification - Individuals that are diagnosed with thalassemia minor have inherited the disorder from only one parent, making them heterozygous for the condition.