Hemoglobin electrophoresis is normal with increased levels of Hgb Bart's if the cord blood is electrophoresed. Only one of the four genes is abnormal. As a result there is a near normal production of alpha chains with very few if any clinical or laboratory changes. The gene controlling delta chain production is located very close to the beta gene on chromosome 11. If one gene is deleted then the other may be affected.
Most patients survive to adult life with minimal transfusion requirements.
L Morphology - hypochromic microcytic with marked anisocytosis and poikilocytosis. Erythrocyte inclusions are common. The indecies are discordant. This is a mixup in the production of the non-alpha chain. The carbon end is the amino acid sequence of the delta chain while the N-terminal end is the amino acid sequence of the beta chain.