X-Linked Agammaglobulinemia

Synonyms

Agammaglobulinemia- X-linked- type 2
XLA
X-Linked Hypogammaglobulinemia
Bruton type agammaglobulinemia
Bruton syndrome
Sex-Linked Agammaglobulinemia

Overview

X-linked agammaglobulinema is a genetic condition that affects the immune system and occurs almost exclusively in males. Affected individuals have very few B cells in the body, which produce antibodies called immunoglobulins that help protect the body against infection. Those with this condition are more susceptible to infections because their body makes very few of these antibodies.This condition is inherited in an X-linked recessive pattern and is caused by mutations in the BTK gene. 

It occurs in a frequency of about 1 in 100,000 male newborns, and has no ethnic predisposition. XLA is treated by infusion of human antibody. Treatment with pooled gamma globulin cannot restore a functional population of B cells, but it is sufficient to reduce the severity and number of infections due to the passive immunity granted by the exogenous antibodies.

Symptoms

  • Frequent pus-producing infections
  • Inner ear infections
  • Lung infections
  • Sinus infections
  • Pneumonia
  • Missing tonsils
  • Missing adenoids
  • Delayed growth
  • Slow height gain
  • Abnormality of temperature regulation
  • Decreased antibody level in blood
  • Diarrhea
  • Inflammatory abnormality of the eye
  • Otitis media
  • Recurrent cutaneous abscess formation
  • Recurrent respiratory infections
  • Short stature
  • Sinusitis
  • Skin rash
  • Skin ulcer

Affected infants are usually healthy for the first few months of life until they begin to develop recurrent bacterial infections. The most common bacterial infections are ear infections, pneumonia, pink eye, sinus infections, and infections that cause chronic diarrhea. These bacterial infections can be severe and life-threatening. Most affected individuals are not vulnerable to infections caused by viruses. Infections can usually be prevented with proper treatment.

Causes

XLA is caused by a mutation on the X chromosome of a single gene identified in 1993 which produces an enzyme known as Bruton's tyrosine kinase, or Btk. XLA was first characterized by Dr. Ogden Bruton in a ground-breaking research paper published in 1952 describing a boy unable to develop immunities to common childhood diseases and infections. It is the first known immune deficiency, and is classified with other inherited (genetic) defects of the immune system, known as primary immunodeficiency disorders.

Diagnosis

The list of diagnostic tests mentioned in various sources as used in the diagnosis of X-Linked Agammaglobulinemia includes:

  • Immune function blood tests
  • B-cell level blood test
  • Immunoglobulin levels blood test
  • Antibody tests - antibodies to specific germs are missing

Treatment

Managing X-linked agammaglobulinemia (XLA) mainly consists of preventing infections and treating infections aggressively when they do occur. Sudden infections in individuals with XLA are usually treated with antibiotics that are taken for at least twice as long as taken in healthy individuals. Preventing bacterial infections is very important for people with XLA. Gammaglobulin (a type of protein in the blood that contains antibodies to prevent or fight infections) is the main treatment for people with XLA. In the past, most people received this by intravenous (IV) infusion every two to four weeks. However, in the last few years, an increasing number of people have been receiving it by weekly subcutaneous injections. The choice of whether to receive it intravenously or by injection may just depend on what is most convenient for the doctor and/or patient. Sometimes, people with XLA have a reaction to gammaglobulin, which may include headaches, chills, backache, or nausea. These reactions are more likely to occur when they have a viral infection or when the brand of gammaglobulin has been changed. Some centers use chronic prophylactic antibiotics (continuous use of antibiotics) to prevent bacterial infections.

Aggressive use of antibiotics lower the chance of chronic sinusitis and lung disease, which are common complications in individuals with XLA. Early diagnosis and treatment of bowel infections may decrease the risk of inflammatory bowel disease (IBD). Furthermore, children with XLA should not be given live viral vaccines. For example, they should be given inactivated polio vaccine (IPV) rather than the oral polio vaccine. The siblings of children with XLA should also be given inactivated polio vaccine (IPV) rather than oral polio vaccine in order to avoid infecting their affected sibling with live virus.