Do you or your child often get respiratory infections or find that your infections are hard to clear, even with treatment? These can be signs of specific antibody deficiency (SAD), a mild type of primary immunodeficiency (PI), also called inborn errors of immunity (IEI). SAD causes repeated infections, but they’re usually less severe than those seen with other types of PI.

Even when they’re mild, recurrent infections can have a big impact on your or your child’s quality of life. The good news is that some children outgrow their SAD, and effective treatment is available for those who have it for life. This article provides an overview of SAD, including its causes, symptoms, and treatments.

What Is Specific Antibody Deficiency?

People with SAD generally have normal levels of antibodies (also called immunoglobulins), which isn’t the case for people with other primary immunodeficiencies. However, their immune systems can’t produce antibodies to certain illness-causing germs (like specific viruses and bacteria). Without the right antibodies, they’re at an increased risk of getting sick from these germs.

Normally, when a person is exposed to a virus or bacteria that can make them sick, their bodies naturally produce protective antibodies. This can happen because they’ve come into contact with the virus or bacteria naturally or because they’ve received a vaccine against it.

People with SAD may not develop the antibody after getting the vaccine, so they can get sick with specific illnesses even if they’ve been vaccinated against them. Other parts of the immune system can still work together to fight these illnesses, so some people with SAD still rarely get sick, or they recover from illness somewhat easily.

Symptoms of Specific Antibody Deficiency

Some children start showing signs of SAD in their first year of life, while for others, the recurrent infections start later in life. Recurrent infections are the main symptom of SAD, and most people with SAD experience multiple types of infections repeatedly. The following infections are the most common:

Sinus Infections

A sinus infection, or sinusitis, is an infection affecting the sinuses (air-filled and mucus-producing cavities in your nose, cheeks, and forehead). These infections can come from viruses or bacteria that cause inflammation in your sinuses.

Research shows that around 64 percent of people with SAD experience chronic or recurrent sinus infections. These recurrent sinus infections can involve:

• Tiredness
• A stuffy nose
• A runny nose
• A sour taste in your mouth
• Mucus dripping down your throat
• Pressure in your face, head, and ears

Ear Infections

SAD can also cause recurrent or chronic ear infections, with around 35 percent of people with SAD reporting ear infections as a symptom. Generally, ear infections are much more common in children than adults, especially when children are under 2 years old.

Ear infections happen when bacteria or viruses infect the fluid around your eardrum. This causes inflammation that can lead to a variety of symptoms:

• Ear pain
• Trouble hearing
• Feeling like your ear is blocked
• Drainage out of the infected ear
• A feeling of pressure in the ear
• Fever

Respiratory Infections

Upper and lower respiratory infections are among the most common recurrent infections in people with SAD. Recurrent respiratory tract infections are a diagnostic criterion for SAD, which means you must experience them to be diagnosed. There are multiple types, but these are the most common:

Pneumonia

Research suggests that 62 percent of people with SAD experience pneumonia, which can be a viral, bacterial, or fungal infection of the lungs. Pneumonia causes inflammation and fluid accumulation in the small air sacs inside the lungs, which are called alveoli.

Pneumonia symptoms range from mild to severe and can include high fever, coughing up mucus, and chest pain with deep breathing. People with SAD who have asthma, a condition associated with SAD, are at an even higher risk of recurrent bacterial pneumonia infections.

Bronchitis

Roughly half of people with SAD have bronchitis, which is inflammation in the airways leading to your lungs and often develops after a respiratory infection. The main symptom of bronchitis is a persistent cough. Sometimes it’s a dry cough, but in other cases, you may cough up mucus.

Acute bronchitis usually comes from a viral infection. If bronchitis becomes chronic, it can remain for the rest of your life but is manageable. Recurrent or chronic bronchitis is common among people with SAD.

SAD Complications

You may develop complications as a result of the recurrent infections associated with SAD. The goal of treatment is to prevent permanent damage to your ears, sinuses, lungs, and other areas affected by recurrent infections.

Hearing Loss

Chronic or recurrent ear infections may cause permanent hearing loss. This can happen if the recurrent inflammation in the ear damages the eardrum or other structures involved in hearing. It’s especially risky for small children with SAD because hearing loss may result in speech delays.

Chronic Lung or Sinus Diseases

Chronic lung disease with scarring can occur because of chronic or recurrent lung infections in people with SAD. Chronic rhinosinusitis (long-term inflammation of the sinuses) can also result from recurrent infections in SAD.

Bronchiectasis

Bronchiectasis, a lung complication from SAD, may be preventable with treatment for repeated respiratory infections. It happens when your airways become widened, which makes it harder to inhale and exhale. Bronchiectasis can cause mucus to get trapped in your lungs, leading to further infections, inflammation, and damage.

How Specific Antibody Deficiency Is Treated

If you or your child has SAD, it’s important to work closely with your doctor to reduce the frequency of infections and treat them as they occur. Your doctor can also treat you or your child for noninfectious conditions commonly linked to SAD, such as asthma and eczema.

Antibiotics

Antibiotics are medications that can treat bacterial infections, including common SAD infections like ear and sinus infections. Antibiotics can help lower the risk of SAD complications while also reducing symptoms so you or your child can avoid missing school or work. In some cases, doctors prescribe preventive antibiotics to stave off bacterial infections before they start.

Revaccination Strategies

If your child has SAD, their immunologist may evaluate them regularly as they grow up to see if they still have SAD. Some children outgrow the condition while others must manage it long term. Some evaluations can involve revaccinating the child with certain vaccines and checking if they develop antibodies in response.

Managing Coexisting Conditions

Around 50 percent of people with SAD have coexisting conditions like atopic eczema or asthma. You’ll need to manage these conditions alongside SAD, which can involve anti-inflammatory treatments like corticosteroids or biologics.

Immunoglobulin Replacement Therapy

Immunoglobulin (Ig) replacement therapy isn’t as commonly used for SAD as it is for other types of PI. In severe cases, doctors might recommend this treatment as a way of providing your body with the specific antibodies it cannot make on its own.

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