Re: What is haemoglobin G? Is this an abnormal haemoglobin?

Tracy,

Thank you for your very interesting question! We will probably entertain lively feedback concerning this question and answer.

Normal hemoglobins (Hb) in the red cell are Hb B, Hb A1, Hb F, and Hb A2. Hemoglobin G is considered abnormal hemoglobin in that it deviates from the accepted hemoglobins. However, there is no recorded clinical consequence to the patient presenting with Hemoglobin G.

So… “Just how abnormal is Hb-G?” may be your actual question. “Abnormal” may well be determined by the investigator defining it depending on the connotation of genetic variance or patient clinical outlook. A genetics scientist will say, “Hb-G is variant and abnormal.” A physician scientist will say, “My patient is fine! So who cares?”

As a memory refresher: Hemoglobin is the red oxygen-carrying pigment of erythrocytes, formed in bone marrow. It contains four heme groups and globin subunits and is capable of reversible oxygenation. A molecule of hemoglobin contains four polypeptide globin chains, composed of between 141 and 146 amino acids. Different types of hemoglobins are determined by different combinations of chains or by mutations causing differences in the amino acid sequence in a globin chain.

Hemoglobin G Philadelphia (Hb-G Phil) is an alpha globin chain variant. It is the most common alpha chain variant in African Americans. Certain electrophoretic characteristics are similar to Sickle Hemoglobin, causing occasional misdiagnosis of sickle cell anemia.

Hemoglobin G-Phil, by itself, has no clinical consequences. Individuals should be reassured that there are no clinical problems.

There are rare examples of other hemoglobin diseases in association with Hb G-Phil. Genetic counseling may or may not be indicated, depending on testing of the actual variants associated with Hb-G Phil. Hopefully my response and the references below may help you decide on your answer as to genetic variation normalcy versus clinical picture normalcy.

Good Luck!

Peter

References:

1. http://www.scinfo.org/hemoglb.htm#HEMOGLOBIN%20G%20-%20PHILADELPHIA

2. http://health.state.ga.us/programs/nsmscd/occasional.asp

3. http://iweb.lati.tec.sd.us/STAFF/GLEYSTEM/webpage/hematology/REDBLOODCELLS.htm

4. http://www.ann.jussieu.fr/~thiriet/csas/Glosr/Bio/BioMolec/Hb.html (Note, this site is in French.)

[Moderator's Note: A large number of Hemoglobin variants (alleles) bear the name Hemoglobin G, and these are distinguished by a suffixed placename like "(Philadelphia)". The Hemoglobin G (Philadelphia) gene is an Alpha-2 (A2) gene variant characterized by a ASN to LYS change at residue 68. While all A2 Hemoglobin G variants appear to share this mutation, there are several distinct Alpha-1 (A1) and Beta (B) gene variants with this name. You can find copious information about these variants on the NIH's Online Mendelian Inheritance in Man (OMIM) database. Here are direct links to the pages for Alpha-1 variants, Alpha-2 variants, and Beta variants. If you search these pages for "Hemoglobin G" you will find the information in question.]