Hemoglobin C

It was my nephew's second visit to the doctor and I decided to accompany my sister to the appointment. The pediatrician took his weight, length and checked his reflexes and we were happy to hear that all was well. As my sister dressed her son the doctor returned to the room. Expressionless, he held onto a piece of paper which alarmed us both. The doctor informed us that he had finally received her son's blood work from the hospital. We stared at the lab results, wondering one thing - was her son okay?

The doctor told us that he tested positive for hemoglobin C. Further testing showed that my sister passed along the hemoglobin C trait to her son and her husband passed on the normal hemoglobin A trait.

What is hemoglobin C? The C gene for hemoglobin is a variant form. Hemoglobin is an iron-carrying protein structure found in red blood cells. It is a tetramer composed of two alpha and two beta chains and it works by picking up oxygen from the lungs and carrying it to the body's tissues.

Normal forms of hemoglobin (Hb) include:
Hemoglobin A - this is the normal adult form that contains a pair of alpha and beta chains
Hemoglobin A2 - makes up approximately 3% of hemoglobin and is found in adults; it forms in the fetus during the third trimester and is composed of a pair of alpha and delta chains
Hemoglobin F - is fetal hemoglobin which begins to decline after birth and contains two alpha and two gamma chains; the classic hemoglobin "switch" to adult hemoglobin A occurs at six months of age

Now, where does hemoglobin C fit into all of this? Hemoglobin C is one of the many variants of hemoglobin. This trait is found most commonly in West Africans. It also occurs in about 3% of African-Americans. As mentioned in my nephew's case, the C trait is passed on by one parent. The child has one normal and one abnormal trait resulting in a hemoglobin gene described as HbAC.

So, should parents be concerned about this condition? No, hemoglobin C will not lead to disease. There is usually no medical treatment required as the majority of people with hemoglobin C go on to live normal lives. However, some symptoms have been found to occur such as mild anemia, a slightly enlarged spleen and gallstones.

Fortunately, the disease is not similar to sickle cell anemia. Sickle cell anemia is a serious disease marked by a defect in the gene sequence of the beta chain due to an amino acid switch. Hemoglobin in people with sickle cell anemia is denoted as HbSS. This defect in genetic coding leads to a structural change of red blood cells known as sickling. The shape changes from biconcave red blood cells to a sickle. The sickling will cause red blood cells to hook into each other, build up into clumps and get trapped in blood vessels. The trapped cells result in partial or complete blockage of blood vessels which leads to poor blood flow. In sickle cell patients, the oxygen-deprived tissue is not only painful but causes disease and infection.

Hemoglobin C disease is not as serious as sickle cell anemia. However, it should not be ignored either. It is important for people with a history of anemia to get genetic counseling when considering having a child. For instance, if someone with Hemoglobin C disease (HbAC) has a child with someone who is only a carrier for the sickle cell trait (HbAS) they have a 25% chance of having a child with Hemoglobin SC (HbSC) disease. This disease will manifest into a serious medical condition because it is a form of sickle cell. Patients need close medical monitoring since they will develop symptoms such as enlarged spleens, sickle cell crisis, infections and stroke.

Sources: http://www.nlm.nih.gov/medlineplus/ency/article/000572.htm, http://sickle.bwh.harvard.edu/hemoglobin.html, http://www.uihealthcare.com/topics/medicaldepartments/pediatrics/hemoglobinc/index.html