Hemoglobin A (the major hemoglobin in adults) contains alpha-globin and beta-globin chains.
In alpha thalassemia, there is a reduced amount of alpha-globin chains.
Types
Two types of alphathalassemiacan lead to health problemsHb Bart syndrome and HbH disease.
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Hb Bart Syndrome
This syndrome is the most severe form of alpha thalassemia.
It is also known as hemoglobin Bart hydrops fetalis syndrome and alpha thalassemia major.
In this syndrome, excess fluid builds up in a fetuss body before birth.
It can cause:
Most babies born with Hb Bart syndrome are stillborn or die shortly after birth.
In addition, the condition can cause pregnancy complications, including preeclampsia, premature birth, and bleeding.
HbH Disease
Hemoglobin H (HbH) is the milder form of alpha thalassemia.
The symptoms usually appear in early childhood.
The condition may cause:
People with HbH disease usually live into adulthood.
Symptoms
Alpha thalassemia symptoms vary depending on the severity of the disease.
Therefore, the risk of having a child with alpha thalassemia disease depends on the status of the parents.
People have four alpha-globin proteins that form theHBA1and theHBA2genes (calledalleles).
When some or all of these alleles are missing, alpha thalassemia occurs.
The risk is as follows:
Thousands of babies are born with alpha thalassemia every year.
It is most prevalent in Asia, Africa, and the Mediterranean area.
Approximately 30% of African-Americans have either alpha thalassemia silent or alpha thalassemia trait.
Diagnosis
Diagnosing alpha thalassemia depends on the severity of the disease.
Alpha thalassemia is usually suspected after a persons child is born with HbH disease.
Doctors can diagnose silent carriers with genetic testing.
A problem usually comes to light during a routine CBC.
The CBC will reveal a mild to moderate anemia with very small red blood cells.
Small red blood cells can beconfused with iron deficiency anemia.
If necessary, a doctor can confirm this with genetic testing.
Doctors can identify hemoglobin H on the newborn screen as well.
A hematologist will monitor children with this diagnosis, closely.
In addition, some patients are identified later in life during a work-up for anemia.
Hb Bart Syndrome
Hydrops fetalis is not a specific diagnosis but rather characteristic features on aneonatal ultrasound.
In Hb Bart syndrome, four alpha-globin genes are missing.
Although, people with alpha thalassemia minor will have lifelong mild anemia.
Those with more moderate to severe cases may requireblood transfusionsorchelation therapy.
Transfusions
People with HbH disease usually have moderate anemia that is well-tolerated.
However, transfusions are occasionally needed during illnesses with a fever due to accelerated red blood cell breakdown.
Adults may require more regular transfusions.
Iron Chelation Therapy
People with HbH disease may developiron overload.
Medications called chelators can help rid the body of excess iron.
Summary
Alpha thalassemia is an inherited disorder in which the body can not produce enough hemoglobin.
The condition ranges from asymptomatic to severe.
Sometimes, a person can be a carrier (silent alpha thalassemia) with no sign of disease.
Others may have very mild disease, known as having alpha thalassemia trait.
The two types of alpha thalassemia that cause health problems are Hb Bart syndrome and HbH disease.
Hb Bart syndrome is diagnosed prenatally and is fatal before birth or shortly after.
HbH disease is often diagnosed in childhood.
However, people with HbH live well into adulthood.
Genetic testing can confirm if you are a silent carrier.
Talk to your doctor if you are concerned about alpha thalassemia.
They may recommend genetic testing and blood work.
National Institutes of Health: Genetic and Rare Diseases Information Center.Alpha-thalassemia.
National Organization for Rare Disorders.Alpha thalassemia.
National Library of Medicine: MedlinePlus.Alpha thalassemia.
2017;10(12):1087-1094. doi:10.1080/17474086.2017.1395279
