What Is Hb H Disease?

Medically Reviewed on 2/7/2023

Illustration of hemoglobin blood cells
Hb H disease is an inherited hemoglobin disorder that causes an excess of beta-globin chains that destroy the red blood cells.

Hemoglobin H (Hb H) disease is an inherited hemoglobin disorder in which three out of the four alpha-globin genes that are usually present are deleted or has a mutation that impairs alpha-globin chain production. This leads to an excess of beta-globin chains that are unstable, precipitate within the cell, and destroys the red blood cells.

Hb H is a thalassemia-like syndrome defined by hemolysis and the production of ineffective red cells. Co-inheritance of Hb H with other globin gene defects can have an effect on the severity of the condition.

What causes Hb H disease?

Because hemoglobin H (Hb H) is a hereditary disorder, parents can pass on the defective genes to their offspring. To develop Hb H disease, a person must inherit the genes from both parents.

What are the signs and symptoms of Hb H?

Top phenotypes and signs associated with hemoglobin H include

What is the Hb H gene related to HBA1 and HBA2?

  • Alpha-globin is made by HBA1 and HBA2. This protein is also produced by HBA1 and HBA2. These two alpha-globin genes are located near each other on chromosome 16.
  • Alpha-globin is a smaller protein found in red blood cells, which provides oxygen to cells and tissues. Hemoglobin is composed of four subunits, two of which are alpha-globin.
  • Fetal hemoglobin, which is active from birth to newborn, and adult hemoglobin, which lasts a lifetime, both contain alpha-globin.
  • Hemoglobin consists of four subunits, each carrying a heme molecule. To absorb oxygen from the lungs and transfer it to the tissues, red blood cells need heme molecules. Hemoglobin can carry four oxygen molecules at once (one attached to each heme molecule). The vivid red color of blood comes from hemoglobin that contains oxygen.

What are the treatment options for Hb H?

  • Patients with hemoglobin H disease can range widely in clinical severity, so it's critical to get an early diagnosis so that patients can be monitored. Regular monitoring of the patient's growth and development and hemoglobin levels is necessary.
  • Moreover, assessment of persistent hemolysis-related complications is necessary so that any significant decline in hemoglobin may be identified and treated.
  • Infections should be continuously monitored. Additionally, monitoring health and keeping up with vaccinations as needed is essential. For many patients with the condition, maintaining their health requires frequent blood transfusions and iron chelation.


Sickle cell disease is named after a farming tool. See Answer

The physiology of Hb H disease

  • As a result of decreased alpha-globin chain synthesis, extra beta chains build up and combine to create nonfunctional hemoglobin H (Hb H) and less hemoglobin A (HbA).
  • Red blood cells that are hypochromic and microcytic are created when HbA levels are low. Additionally, the creation of Hb H results in red blood cells that are sensitive to oxidative stress, which leads to an increase in the destruction of red blood cells.
  • Essentially, Hb H disease is a hemolytic condition. Mothballs, viruses and oxidizing medicines can all make hemolysis worse.

What are the diagnostic methods?

Hemoglobin H (Hb H) disease should be considered in babies and children who have mild-to-moderate microcytic hypochromic hemolytic anemia and hepatosplenomegaly. Blood smears stained with cresyl blue can be examined for Heinz’s bodies. Hb H (5 to 30 percent) is present, according to the Hb biochemical assay. Genetic testing is used to confirm the diagnosis.

Differential diagnosis

  • Alpha-thalassemia X-linked intellectual deficiency and other hemolytic anemias are among the differential diagnoses.

Antenatal diagnosis

  • When a severe type of Hb H disease has been previously detected in a family member, prenatal diagnosis is possible.

Follow-up after diagnosis confirmation

Following a confirmed diagnosis of Hb H disease, patients should adhere to the following guidelines:

  • Regular appointments with a child's hematologist.
  • Parents need to be aware that Hb H disease is a chronic condition that necessitates ongoing monitoring of hemoglobin levels, growth and development.
  • Give a list of available resources, such as the regional health department, early intervention service providers, and the Children's Memorial Hospital Comprehensive Thalassemia Program.
  • To assist the parents in understanding the complexities of the carrier state and inheritance of this disease, genetic counseling services are advised.
  • The National Newborn Screening and Genetics Resource Center, 1912 W, may provide further information regarding newborn screening in general and Hb H.

Transfusion therapy

Hemoglobin levels in HCS patients might drop quickly as a result of common infectious infections such as the flu or viral fever. Patients with Hb H experience substantially less hemoglobin loss, making the development of severe anemia requiring transfusions improbable.

Hemoglobin levels lower than 6 g/dL require transfusions. In stabilized patients with Hb values between 6 and 10 g/dL, clinical status is the deciding factor; patients with values higher than 10 g/dL rarely require transfusion. If a patient requires frequent transfusions, splenectomy is advised.

Chronic transfusion therapy, such that provided to those with beta-thalassemia major, has little place in medical practice.

Iron surcharge

Adults with Hb H experience iron overload. Early iron excess in HCS may require treatment.


Overall survival is variable but typically good. Most individuals live into adulthood although some have more challenging courses of treatment.
Medically Reviewed on 2/7/2023
Image source: iStock Images

HBA1 gene https://medlineplus.gov/genetics/gene/hba1/

HBA2 gene https://medlineplus.gov/genetics/gene/hba2/

Hb H disease: clinical course and disease modifiers


Hemoglobin H Disease https://dph.illinois.gov/content/dam/soi/en/web/idph/files/publications/alpha-thal-fact-sheet-08.pdf