X-Linked Agammaglobulinemia (XLA): Symptoms & Treatment

Quick answer: X-linked agammaglobulinemia (XLA) is a rare inherited immune disorder, almost always in boys, in which the body cannot make B cells or the antibodies they produce. It is caused by a change in the BTK gene on the X chromosome. Babies are usually healthy for the first few months thanks to antibodies from their mother, then start getting repeated bacterial infections, often between 6 and 9 months of age, such as ear and sinus infections, pneumonia and, in severe cases, meningitis or sepsis. XLA is diagnosed with blood tests showing very low antibody levels and almost no B cells, and confirmed with genetic testing. There is no cure, but lifelong immunoglobulin (antibody) replacement, given as IVIG every 3 to 4 weeks or SCIG at home usually weekly, plus prompt antibiotics lets most children lead normal, active lives.

What is X-linked agammaglobulinemia (XLA)?

X-linked agammaglobulinemia is a primary immunodeficiency, meaning a child is born with an immune system that doesn’t work properly. In XLA, the body can’t make mature B cells, the white blood cells that produce antibodies (also called immunoglobulins or gamma globulins). Without antibodies, a child can’t fight off many bacteria and some viruses.

The name describes the condition: “X-linked” because the gene is on the X chromosome, and “agammaglobulinemia” because there are almost no gamma globulins (antibodies) in the blood. It is also called Bruton’s agammaglobulinemia or Bruton disease, after Dr. Ogden Bruton, who described it in 1952. XLA was the first immunodeficiency disease ever identified.

XLA is rare. It affects about 1 in 200,000 newborns, or roughly 1 in 100,000 boys. To learn about other conditions in this group, see our overview of immunodeficiency disorders in children.

XLA at a glance

Topic	Key facts
Cause	A change (variant) in the BTK gene, which makes Bruton tyrosine kinase, a protein B cells need to develop
Who gets it	Almost always boys; inherited in an X-linked recessive pattern
How common	About 1 in 200,000 newborns (roughly 1 in 100,000 boys)
When symptoms start	Usually 6 to 9 months of age; sometimes not until 3 to 5 years
Main symptoms	Repeated bacterial infections: ear, sinus, lung, skin and eye infections; chronic diarrhea
Key tests	Very low IgG, IgA and IgM; fewer than 1 to 2% B cells (CD19+); BTK genetic testing
Treatment	Lifelong immunoglobulin replacement (IVIG or SCIG) and prompt antibiotics
Vaccines to avoid	Live vaccines, such as MMR, chickenpox (varicella), rotavirus and oral polio
Outlook	With early diagnosis and treatment, most children lead normal, active lives into adulthood

What causes XLA?

XLA is caused by a variant in the BTK gene. This gene gives instructions for making a protein called Bruton tyrosine kinase, which immature B cells need in order to grow into mature, antibody-making cells. Most BTK variants stop the body from making any working BTK protein, so B cell development stalls in the bone marrow and the child ends up with very few antibodies.

XLA is not contagious, and nothing a parent did during pregnancy causes it.

Symptoms of XLA in babies and children

Newborns with XLA usually seem healthy at first, because antibodies passed from the mother during pregnancy protect them for the first few months. As those borrowed antibodies fade, infections begin. Symptoms most often start between 6 and 9 months of age, although some children aren’t affected until 3 to 5 years old. On average, children are diagnosed at about 2.5 years, and nearly all are diagnosed before age 5.

Common signs include:

Repeated ear infections (otitis media) and sinus infections
Lung infections, such as bronchitis and pneumonia, often needing IV antibiotics or a hospital stay
Pink eye (conjunctivitis) and skin infections
Chronic diarrhea, sometimes from the parasite Giardia
Infections that take longer than usual to clear or keep coming back, even with antibiotics
Very small or absent tonsils and lymph nodes that can’t be felt, because these tissues are normally full of B cells
Poor weight gain or slow growth from repeated illness

More serious infections can include meningitis, sepsis (a bloodstream infection), and bone or joint infections. Children with XLA are also at risk of severe, long-lasting infections of the brain from enteroviruses, such as echovirus and coxsackievirus.

The bacteria behind most XLA infections are “encapsulated” germs such as Streptococcus pneumoniae, Haemophilus influenzae and Staphylococcus aureus.

How is XLA inherited?

XLA follows an X-linked recessive pattern. Boys have one X chromosome, so one changed copy of the BTK gene is enough to cause XLA. Girls have two X chromosomes, so a working copy on the other X usually protects them. That is why XLA affects boys almost exclusively.

A mother who carries the gene change has a 50% chance with each pregnancy of passing it on. Sons who inherit it will have XLA; daughters who inherit it will be carriers.
A father with XLA cannot pass it to his sons, but all of his daughters will be carriers.
About half of children with XLA have no family history of the condition. In most of these cases, the gene change is new in the child.

Genetic counseling is recommended for families. Testing can show which female relatives are carriers, and prenatal testing is available when the family’s gene change is known.

How is XLA diagnosed?

Doctors suspect XLA in a boy with repeated or severe bacterial infections, especially infections that need IV antibiotics, plus clues such as missing tonsils or a family history. Diagnosis usually involves:

Immunoglobulin levels: a blood test showing very low IgG, IgA and IgM antibodies for the child’s age.
B cell count (flow cytometry): a blood test showing that fewer than 1 to 2% of lymphocytes are mature B cells (measured as CD19+ or CD20+ cells).
Vaccine response: little or no antibody response after routine inactivated vaccines.
Genetic testing: finding a disease-causing variant in the BTK gene, or low or absent BTK protein, confirms the diagnosis.

Abnormal results are usually repeated to confirm them before treatment starts. Doctors also rule out conditions that can look similar, such as common variable immunodeficiency (CVID), autosomal recessive agammaglobulinemia, transient hypogammaglobulinemia of infancy and severe combined immunodeficiency (SCID).

XLA vs. CVID: what’s the difference?

	XLA	CVID
Cause	Variant in the BTK gene	Usually unknown; many possible genes
Who	Almost always boys	Boys and girls equally
Typical onset	Infancy or early childhood	Often later childhood or adulthood
B cells	Almost none	Usually present but don’t make enough antibodies
Main treatment	Immunoglobulin replacement	Immunoglobulin replacement

How is XLA treated?

There is no cure for XLA yet, but treatment works well. Care is usually led by a pediatric immunologist and focuses on preventing and treating infections.

Immunoglobulin replacement therapy

The main treatment is lifelong immunoglobulin (IgG) replacement, which gives your child the antibodies their body can’t make. The antibodies come from donated, purified blood plasma. There are two ways to give it:

IVIG (intravenous immunoglobulin): given through a vein, usually every 3 to 4 weeks, at an infusion center, clinic or sometimes at home.
SCIG (subcutaneous immunoglobulin): given under the skin, usually once a week or more often, and can be done at home by parents after training. It tends to keep antibody levels steadier and causes fewer whole-body side effects.

Both are first-line options. The doctor adjusts the dose based on your child’s weight, blood antibody levels and how well infections are controlled.

Antibiotics

Infections should be treated promptly and fully with antibiotics. Some children also take daily preventive antibiotics, especially if they have lung damage.

Vaccines

Children with XLA should not receive live vaccines, such as MMR (measles, mumps, rubella), chickenpox (varicella), rotavirus, oral polio, BCG or yellow fever. The live oral polio vaccine in particular can cause a persistent infection in children with XLA. Inactivated vaccines are generally safe, though they may not produce much protection on their own. Your child’s immunologist will guide which vaccines to give. Learn more about why measles protection matters for the whole family.

Treatments being studied

Stem cell (bone marrow) transplant and gene therapy are being studied for XLA but are not standard treatments.

Complications of XLA

Chronic lung disease and bronchiectasis (permanent widening and scarring of the airways) from repeated pneumonia. This is the most common long-term complication, which is why early diagnosis matters.
Persistent enterovirus infections of the brain and nervous system
Joint problems that can look like juvenile arthritis
Autoimmune and inflammatory conditions, which are less common
A small increased risk of certain cancers, such as colon cancer and lymphoma, reported in older patients

What is the outlook for children with XLA?

Before immunoglobulin therapy was available, most children with XLA died before age 10. Today the outlook is very different. Children who are diagnosed early (before age 5) and treated consistently can usually lead normal, active lives, go to school, play sports and live well into adulthood. Experts note that isolation is generally not needed. Chronic lung disease is the main factor that can affect long-term health, so keeping up with infusions and treating infections quickly is key.

Living with XLA: tips for families

Stay on schedule with IVIG or SCIG; skipped doses let antibody levels drop.
Act fast on fevers and infections. Ask your immunologist for a clear plan on when to call.
Tell every provider and school that your child has XLA and must not get live vaccines.
Keep the family’s vaccines up to date as your immunologist advises, to help shield your child.
Practice good hygiene: handwashing, and safe food and water to lower the risk of Giardia and other gut infections.
Support emotional health. A chronic condition affects the whole family; patient groups and counselors can help.

When to call the doctor

Talk to your pediatrician about immune testing if your child, especially a boy:

Has repeated ear, sinus or lung infections, or infections that don’t clear with usual antibiotics
Has needed IV antibiotics or a hospital stay for an infection
Has pneumonia more than once
Isn’t gaining weight or growing as expected
Has a family history of XLA or another immune disorder

If your child has XLA, get medical care right away for any fever, a stiff neck, severe headache, unusual sleepiness or confusion, trouble breathing, or a child who seems very sick. See our red-flag guide for parents. Need a specialist? Use our pediatrician directory to find care near you.

Frequently Asked Questions

Can girls get X-linked agammaglobulinemia?

Very rarely. Because the gene is on the X chromosome and girls have two X chromosomes, a working copy usually protects them, so girls are typically carriers rather than affected. A similar condition called autosomal recessive agammaglobulinemia can affect girls and boys.

What is the life expectancy of someone with XLA?

With early diagnosis and lifelong immunoglobulin replacement, most people with XLA live well into adulthood and lead active lives. Before treatment existed, most children died before age 10. Chronic lung damage from repeated infections is the main factor that can shorten life, so consistent treatment matters.

At what age do XLA symptoms start?

Symptoms usually start between 6 and 9 months of age, after the antibodies a baby received from the mother wear off. Some children don’t have symptoms until 3 to 5 years old. Most children are diagnosed by age 5.

Is XLA the same as Bruton’s agammaglobulinemia?

Yes. X-linked agammaglobulinemia is also called Bruton’s agammaglobulinemia or Bruton disease, after Dr. Ogden Bruton, who first described it in 1952. The gene involved is named BTK, for Bruton tyrosine kinase.

Can a child with XLA get vaccines?

Children with XLA should not get live vaccines such as MMR, chickenpox, rotavirus or oral polio. Inactivated vaccines are generally safe, though the child may not make much protection from them. Immunoglobulin replacement provides most of their protection, and their immunologist will advise on vaccines.

Is there a cure for XLA?

Not yet. Lifelong immunoglobulin replacement therapy and prompt antibiotics control the condition well. Stem cell transplant and gene therapy are being studied but are not standard treatments.

How often do children with XLA need IVIG?

IVIG is usually given through a vein every 3 to 4 weeks. Many families choose SCIG instead, which is given under the skin at home, usually once a week. The dose is adjusted based on weight, blood antibody levels and infections.

Can kids with XLA go to school and play sports?

Yes. With regular treatment, most children with XLA can attend school, play sports and take part in normal activities. Isolation is generally not needed, but good handwashing and prompt treatment of infections are important.

Related guides

Sources

Last reviewed October 2026 against the sources above. This article is for general information and is not a substitute for advice from your child’s doctor.