Types of Alpha Thalassemia

Alpha globin is made by four genes and one or more can be mutated or missing, so there are four kinds of alpha thalassemia:
One missing or abnormal gene makes a child a silent alpha thalassemia carrier. Silent alpha thalassemia carriers have no signs or symptoms of the disease, but are able to pass thalassemia on to their children.
Two missing or mutated genes is a condition called alpha thalassemia minor or having alpha thalassemia trait. Children with this condition may have red blood cells that are smaller than normal (microcytosis) and sometimes very slight anemia.

 People with alpha thalassemia minor usually don't have any symptoms at all, but can pass thalassemia on to their children. The two abnormal genes can be on the same chromosome (called the cis position) or one on each chromosome (called the trans position). If two genes on the same chromosome are affected, the person can pass along a two-gene defect to his or her child. This situation is much more common in people of Asian descent.
Three missing or mutated genes is called hemoglobin H disease. Signs and symptoms will be moderate to severe.
Four missing or mutated genes is a condition known as alpha thalassemia major or hydrops fetalis. This almost always leads to a fetus dying before delivery or a newborn baby dying shortly after birth. However if this disease is suspected because of a history in the family, it can be diagnosed prenatally. Sometimes, if treatment is initiated before the baby is even born, the baby can survive.
Complications

In addition to anemia and hydrops fetalis, severe cases of alpha thalasemia and hemoglobin H disease can lead to serious complications, especially if untreated. Complications of alpha thalassemia include:
Excess iron. When children have alpha thalassemia, they can end up with too much iron in their bodies, either from the disease itself or from getting repeated blood transfusions. Excess iron can cause damage to the heart, liver, and endocrine system.
Bone deformities and broken bones. Alpha thalassemia can cause bone marrow to expand, making bones wider, thinner, and more brittle. This makes bones more likely to break and can lead to abnormal bone structure, particularly in the bones of the face and skull.
Enlarged spleen. The spleen helps fight off infections and filters out unwanted materials, such as dead or damaged blood cells, from the body. Alpha thalassemia can cause red blood cells to die off at a faster rate, making the spleen work harder, which makes it grow larger. A large spleen can make anemia worse and may need to be removed if it gets too big.
Infections. Children with alpha thalassemia have an increased risk of infection, especially if they've had their spleens removed.
Slower growth rates. The anemia resulting from alpha thalassemia can cause children to grow more slowly and also can lead to delayed puberty.