Hemoglobin Barts

What it means

Normal adult hemoglobin is composed of two chains each of alpha and beta globin. Hb Barts (Hemoglobin Barts) is a tetramer with four gamma globin chains, and is essentially pathognomonic for one or another form of alpha thalassemia. Hb Barts has an extremely high affinity for oxygen, resulting in almost no oxygen delivery to the tissues.

Hb Bart is normally not present in adult blood. It makes up about 85-90 percent of hemoglobin in Hb Bart hydrops fetalis syndrome, and about 2-5 percent in HbH disease.

Rare diseases that can present with this1

The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions. A sign on this page is a conversation to have with a clinician, not a conclusion.

Part of the broader category

Also called: Haemoglobin Barts · Hb Barts