Hemoglobin C (abbreviated as HbC) is an abnormal hemoglobin in which glutamic acid residue at the 6th position of the β-globin chain is replaced with a lysine residue due to a point mutation in the HBB gene. People with one copy of the gene for hemoglobin C do not experience symptoms, but can pass the abnormal gene on to their children. Those with two copies of the gene are said to have hemoglobin C disease and can experience mild anemia. It is possible for a person to have both the gene for hemoglobin S (the form associated with sickle cell anemia) and the gene for hemoglobin C; this state is called hemoglobin SC disease, and is generally more severe than hemoglobin C disease, but milder than sickle cell anemia.HbC was discovered by Harvey Itano and James V. Neel in 1950 in two African-American families. It has since been established that it is most common among people in West Africa. It confers survival benefits as individuals with HbC are naturally resistant to malaria caused by Plasmodium falciparum,  albeit incompletely. Symptoms and signs
People with one copy of the gene for hemoglobin C (termed heterozygous) do not experience significant symptoms, but can pass the abnormal gene onto their children; this condition is called hemoglobin C trait. When two hemoglobin C genes are present (termed homozygous), the individual is said to have hemoglobin C disease, and may develop mild anemia, as red blood cells containing hemoglobin C have a decreased lifespan.
Epidemiology
Hemoglobin C is found most abundantly in areas of West Africa, such as Nigeria, where Yorubas live. Hemoglobin C gene is found in 2-3% of African-Americans while 8% of African-Americans have hemoglobin S (Sickle) gene. Thus Hemoglobin SC disease is significantly more common than Hemoglobin CC disease. The trait also affects people whose ancestors came from Italy, Greece, Latin America, and the Caribbean region. However, it is possible for a person of any race or nationality to have hemoglobin C trait. In terms of geographic distribution, the hemoglobin C allele is found at the highest frequencies in West Africa, where it has been associated with protection against malaria. Hemoglobin C disease is present at birth, though some cases may not be diagnosed until adulthood. Both males and females are affected equally. History
Studying the molecular basis of sickle cell disease, Linus Pauling and Harvey Itano at the California Institute of Technology discovered in 1949 that the disease was due to abnormal hemoglobin called HBS. In 1950, Itano and James V. Neel discovered from two African-American families a different blood condition very similar to sickle cell disease. Five of the ten individuals indicated sickled RBCs. But the condition was harmless as the individuals had no anaemia. Thus, it was not clear whether it was involved in sickle cell disease. Genetically, the abnormal hemoglobin was only in heterozygous condition. The next year, Neel and his colleagues established that the hemoglobin is associated with sickle cell disease.The hemoglobin was named hemoglobin III, but hemoglobin C was eventually used.