Hemoglobin H disease (HbH) is a blood disorder caused due to mutations in genes responsible for producing hemoglobin, which is a protein present in red blood cells (RBCs). It is responsible for transporting oxygen to all parts of the body.
“HbH disease, which is genetically inherited, is a form of alpha thalassemia. The condition can range from mild to severe. Individuals with mild or moderate form of the condition might not even realise it. Severe cases must get regular blood transfusions,” says Dr Neema Bhat, senior consultant, hematology, BMT physician and paediatric oncology, Apollo Hospitals, Bengaluru.
What causes HbH disease?
HbH disease is genetic in nature. The protein needed to make hemoglobin is produced by four types of genes present in the 16th chromosome (out of the 23 pairs). Mutations in these genes can result in different types of thalassemia. HbH disease is a form of alpha thalassemia.
Who’s at risk?
“Both parents must be carriers of the mutated genes for the child to inherit the condition. If only one parent is a carrier, children may not have the condition,” says Dr Ashish Dixit, consultant, haematology, haemato oncology and bone marrow transplantation, Manipal Hospitals, Bengaluru.
Symptoms of HbH disease
People with the condition usually have lower hemoglobin levels. “Normal hemoglobin levels can be around 12-14 g/dl for females and 13-15 g/dl for males. People having mild form of the condition have a hemoglobin level of 9-10 g/dl or lower. They feel tired most of the time and might suffer from frequent jaundice without infection,” says Dr Bhat.
Diagnosing HbH disease
Individuals having a milder form of the condition usually don’t realise it. They often discover it coincidentally during health check-ups.
“Initially, screening is done through several tests like complete blood count (CBC), peripheral blood smear test (examining blood cells through a microscope) or electrophoresis (biochemical test to check the level of hemoglobin and abnormal red blood cells). During blood tests, thalassemia often mimics iron deficiency. Blood smears for both alpha and beta thalassemia can appear the same. Genetic testing or mutational analysis is done to identify the type of thalassemia,” says Dr Dixit.
Most people having a milder form of the condition live a normal life. “People should follow up with a haematologist every three months after being diagnosed with the condition to check their iron levels as well as kidney and liver functioning,” says Dr Bhat.
She adds, “Severe cases can lead to intrauterine loss of the fetus in pregnant women. Regular blood transfusions are carried out for moderate to severe cases. Bone marrow or hematopoietic stem cell transplantation are recommended for a more permanent solution.”
Children who are going through treatment require special attention to check if their growth is normal.
Dr Bhat advises parents to carry out genetic testing before planning to conceive or even marriage (if possible) to avoid the risk of thalassemia or any other genetically inherited condition. People marrying closely related family members also have a higher risk of inheriting genetic conditions.
- HbH disease, which is a genetically inherited blood disorder, is a form of alpha thalassemia.
- The condition is characterised by low hemoglobin levels and can range from mild to severe.
- Regular health check-ups, blood transfusion and bone marrow transplantation are the available modes of treatment modalities for the condition.