Agammaglobulinemia
Agammaglobulinemia is one of the innate (primary) immune deficiencies. Because of their inability to produce antibodies, affected patients typically have an increased susceptibility to infections in the nose-throat-ear (ENT) area as well as in the lungs. The disease occurs in one in every 50,000 to 100,000 newborns.
What is the cause of agammaglobulinemia?
Agammaglobulinemia is caused by an abnormality in the maturation of B cells. An enzyme – Bruton’s tyrosine kinase (Btk) – is of essential importance for the process of maturation or development of B cells. deficiency of this enzyme, the B cells cannot reach maturity: this results in the non-production or an insufficient production of immunoglobulins.
Genetics and heredity
Agammaglobulinemia is caused by a defect in a sex chromosome (X chromosome). Males have one X chromosome and one Y chromosome. Females have two X chromosomes. The X chromosome is passed down from the mother and the Y chromosome from the father. While agammaglobulinemia occurs in males with a deficient X chromosome, a defect in one X chromosome in females can be compensated by the other non-deficient X chromosome. This is why this disease manifests itself almost exclusively in men.
Symptoms
Predisposition to serious bacterial or viral infections, which generally begin between the sixth and ninth month of life. Bacterial infections of the respiratory tract are particularly common.
If the disease is not treated during childhood: growth retardation; absence of tonsils and lymph nodes; if applicable, chronic skin infections, arthritis (in about 20% of the children concerned).
Diagnostic
Frequent bacterial infections
Absence of mature B cells
Absence of almost all classes of immunoglobulins
The confirmed diagnosis is made by analyzing the child’s X chromosome for defects in the Btk gene.
Treatment with immunoglobulin therapy
Treatment for agammaglobulinemia involves regular injections of immunoglobulin into the body intravenously or subcutaneously to prevent infections. If infections occur, antibiotics may be given. In order to limit the risk of infection on a daily basis, open wounds should be disinfected immediately and all contact with people suffering from contagious infectious diseases should be avoided.
Sources: PinterPandai, NORD – National Organization for Rare Disorders, Mayo Clinic, Immune Deficiency Foundation
Photo credit: XlinkRecessive.jpg: National Institutes of Healthderivative work: Drsrisenthil, Public domain, via Wikimedia Commons
Photo description: the disorder is passed on in an X-linked recessive pattern.
X-linked recessive inheritance is a mode of inheritance in which a mutation in a gene on the X chromosome causes the phenotype to be always expressed in males (who are necessarily homozygous for the gene mutation because they have one X and one Y chromosome) and in females who are homozygous for the gene mutation, see zygosity. Females with one copy of the mutated gene are carriers.
Sources: PinterPandai, NORD – National Organization for Rare Disorders, Mayo Clinic, Immune Deficiency Foundation