Delta-beta thalassemia is a rare form of
thalassemia in which there is a reduced production of
hemoglobin subunit delta and
hemoglobin subunit beta
Hemoglobin subunit beta (beta globin, β-globin, haemoglobin beta, hemoglobin beta) is a globin protein, coded for by the ''HBB'' gene, which along with alpha globin ( HBA), makes up the most common form of haemoglobin in adult humans, hemogl ...
and raised levels of
hemoglobin subunit gamma. It is an
autosomal recessive disorder.
Signs and symptoms
An individual with delta-beta thalassemia is usually asymptomatic, however
microcytosis
Microcytosis or microcythemia is a condition in which red blood cells are unusually small as measured by their mean corpuscular volume.
When associated with anemia, it is known as microcytic anemia.
Causes
Microcytic anemia is not caused by re ...
can occur where the red blood cells are abnormally small.
[
]
Mechanism
Delta-beta thalassemia is autosomal recessive disorder,[ which means both parents are affected and two copies of the ]gene
In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...
must be present. A carrier gets a normal gene to produce hemoglobin A, from one parent and the other parent supplies a gene which makes no hemoglobin A. Delta-beta thalassemia is considered rare.
Delta-beta-thalassemia is caused by deletions of the entire delta and beta genes sequences and only gamma-globin and HbF are formed. Rarely, non-deletional forms have been reported.
When two delta0 mutations are inherited, no hemoglobin A2
Hemoglobin A2 (HbA2) is a normal variant of hemoglobin A that consists of two alpha and two delta chains (α2δ2) and is found at low levels in normal human blood. Hemoglobin A2 may be increased in beta thalassemia or in people who are heterozy ...
(alpha2, delta2) are formed. This is innocuous because only 2-3% of normal adult hemoglobin is hemoglobin A2. The individual will have normal hematological parameters (erythrocyte count, total hemoglobin, mean corpuscular volume). The delta-beta thalassemia demonstrates one mutation is at the +69 position.
Relation to beta thalassemia
Delta-beta thalassemia can mask the diagnosis of beta thalassemia
Beta thalassemias (β thalassemias) are a group of inherited blood disorders. They are forms of thalassemia caused by reduced or absent synthesis of the beta chains of hemoglobin that result in variable outcomes ranging from severe anemia to cl ...
trait. In beta thalassemia, an increase in hemoglobin A2 results, but the co-existence of a delta-beta thalassemia mutation will decrease the value of the hemoglobin A2 into the normal range, thereby obscuring the diagnosis of beta thalassemia trait
Diagnosis
Following the detection of hypochromic
Hypochromic anemia is a generic term for any type of anemia in which the red blood cells are paler than normal. (''Hypo''- refers to ''less'', and ''chromic'' means ''colour''.) A normal red blood cell has a biconcave disk shape and will have an a ...
microcytic red blood cell
Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "holl ...
s, delta-beta thalassemia is confirmed by high-performance liquid chromatography
High-performance liquid chromatography (HPLC), formerly referred to as high-pressure liquid chromatography, is a technique in analytical chemistry used to separate, identify, and quantify each component in a mixture. It relies on pumps to pa ...
.
Treatment
When needed, treatment for anemia
Anemia or anaemia (British English) is a blood disorder in which the blood has a reduced ability to carry oxygen due to a lower than normal number of red blood cells, or a reduction in the amount of hemoglobin. When anemia comes on slowly, t ...
, such as blood transfusions
Blood transfusion is the process of transferring blood products into a person's circulation intravenously. Transfusions are used for various medical conditions to replace lost components of the blood. Early transfusions used whole blood, but mod ...
are used.[
]Stem cell transplant
Hematopoietic stem-cell transplantation (HSCT) is the transplantation of multipotent hematopoietic stem cells, usually derived from bone marrow, peripheral blood, or umbilical cord blood in order to replicate inside of a patient and to produce ...
is another option, but the donor and the individual who will receive the bone marrow transplant must be compatible, the risks involved should be evaluated.
See also
* Alpha thalassemia
Alpha-thalassemia (α-thalassemia, α-thalassaemia) is a form of thalassemia involving the genes ''HBA1'' and ''HBA2''. Thalassemias are a group of inherited blood conditions which result in the impaired production of hemoglobin, the molecule t ...
* Beta-thalassemia
Beta thalassemias (β thalassemias) are a group of inherited blood disorders. They are forms of thalassemia caused by reduced or absent synthesis of the beta chains of hemoglobin that result in variable outcomes ranging from severe anemia to cl ...
* Hemoglobinopathy
Hemoglobinopathy is the medical term for a group of inherited blood disorders and diseases that primarily affect red blood cells. They are single-gene disorders and, in most cases, they are inherited as autosomal co-dominant traits.
There are t ...
References
Further reading
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External links
{{Medicine
Disorders of globin and globulin proteins
Hereditary hemolytic anemias