Alpha geodystrophy is caused by insufficient hemoglobin synthesis due to mutations or deletions in the alpha globin gene, which makes up hemoglobin. Most cases of α-dysplasia are due to deletion of the α gene, and a few are caused by point mutations. The alpha gene is located on chromosome 16, and each chromosome has two alpha genes, so there are four alpha genes in a pair of chromosome 16. According to the number of deletions or mutations of α genes on a single chromosome, we can classify the α gene deletion status into two types: if only one α gene is missing or mutated on one chromosome and the other α gene is normal, the synthesis of the α chain is partially inhibited, which is called α+ paucity; if both α genes on one chromosome are missing or defective, it is called α0 paucity. Then, according to the different combinations of α gene deletion status of a pair (i.e. two) of chromosomes, α-dysplasia is divided into the following categories. 1. Heavy α-dysplasia is a pure state of α0-dysplasia (both chromosomes are in α0 status), i.e., all four α-jugin genes are missing or defective, resulting in no α-chain production at all, and thus the synthesis of HbA, HbA2 and HbF containing α-chain is reduced. The patient cannot synthesize fetal hemoglobin during fetal life, but produces a large amount of γ4 (Hb Bart’s) synthesized by γ chains. Hb Bart’s has a very high affinity for oxygen, causing tissue hypoxia and resulting in fetal edema syndrome. Hb Bart’s is a heterozygous state of α0 and α+ anemia (i.e., one chromosome is α+ and the other is α0), in which there are three α globin genes missing or defective, leaving only one normal α gene. HbH has a high affinity for oxygen and is an unstable hemoglobin, which can be easily degenerated and precipitated in red blood cells to form inclusion bodies, causing stiffness of the red blood cell membrane and making the red blood cells easily destroyed and phagocytosed. It is often clinically manifested as moderate or severe anemia. 3. Mild alpha-geodystrophy is a pure alpha+ geodystrophy (i.e. both chromosomes are in alpha+ status) or alpha0 geodystrophy heterozygous status (i.e. one chromosome is normal and the other is in alpha0 status), both of which have 2 alpha-geodystrophy genes missing or defective and the other two alpha genes are normal, so there is a considerable amount of alpha chain synthesis and the pathophysiological changes are mild. Patients often present clinically with mild anemia. 4. The resting type of α-dysplasia is a heterozygous state of α+-dysplasia (i.e. one chromosome is normal and the other is α+), which has only one α gene deletion or defect, and the synthesis of α chain is slightly reduced, and the pathophysiological changes are very mild. Patients usually do not show clinical symptoms.