Selective IgA deficiency


Selective IgA deficiency, also known as SIgAD, is an inherited condition where the immune system lacks immunoglobulin A (IgA), a crucial protein responsible for combating infections (antibody).

IgA is a protein present in the blood that serves to protect the body against infections occurring in the membranes, which are thin tissues lining various parts of the body such as the eyes, mouth, airways, and digestive system. When someone has selective IgA deficiency, they lack this protein or have very low levels of it, making them vulnerable to infections in these areas. While many people with selective IgA deficiency do not have recurring infections, some might experience issues like pneumonia, ear or sinus infections, allergies, asthma, or diarrhea. People with selective IgA deficiency may be prescribe antibiotics to treat infections.


Selective IgA deficiency typically manifests with no apparent symptoms in most individuals. However, between 25% and 50% of those affected may encounter complications. Some individuals may also experience recurrent and severe infections, particularly affecting the airways, sinuses, ears, mouth, eyes, and digestive tract.

Selective IgA deficiency can present certain complications. Individuals with this deficiency may experience an increased likelihood of allergies and asthma. Additionally, autoimmune disorders can develop, including celiac disease, which damages the small intestine upon gluten consumption, and inflammatory bowel diseases like ulcerative colitis and Crohn’s disease, characterized by inflammation and damage in the digestive tract. Rheumatoid arthritis, involving joint inflammation, and lupus, where the immune system attacks healthy tissue, are also potential complications. In rare instances, receiving blood products containing IgA can trigger a severe allergic reaction known as anaphylaxis, posing a life-threatening risk.


Selective IgA deficiency typically has an inherited pattern, meaning it is passed down through family members who either have selective IgA deficiency or similar immune-related conditions.

Risk factors

Several factors may contribute to one’s risk of developing selective IgA deficiency, such as:

  • Genetics and family history: Having a family member that has selective IgA deficiency or similar immune issue increases the risk of having one.
  • Ethnic background: Estimated around 1 in 500 Caucasians, particularly those of European descent, have this condition.