Primary immunodeficiencies fall into a number of categories: antibody deficiency, cell mediated and combined immuno-deficiencies, complement deficiencies, neutrophil disorders and other associated disorders. Antibody deficiency is present in 80% of cases.

A deficiency of IgA only (selective IgA deficiency) with normal blood levels of IgG and IgM, is the commonest form of antibody deficiency. It occurs in about 1 in 300 people in the UK.

Dr Helen Chapel of the John Radcliffe Hospital, Oxford, provides an overview of the IgA antibody deficiency.

IgA Deficiency: The Medical Background

There are three major families or "classes" of antibodies in the blood.

IgG is the name given to those antibodies which get into tissues as well as blood; therefore they have the most wide-ranging role in preventing infection. They are also the antibodies present in the highest amounts in the blood, which makes them the most important family of antibodies. There are four subclasses of IgG, which are present in varying quantities and one or all may be absent. It is not possible at present to replace the other antibody families (IgA and IgM), but IgG replacement can be given to people who do not make their own IgG antibodies in adequate amounts.

IgM antibodies are bigger than IgG and cannot escape from the blood. They prevent the movement of germs from the blood to other organs such as the brain, liver, spleen, etc. These antibodies are therefore the main ones that protect against brain infections and blood poisoning.

IgA antibodies are those which protect surfaces which come into contact with outside organisms. These surfaces are mainly in the lungs and the gut, and IgA is present in the fluids in these organs.

There are two types of individuals with IgA deficiency: (a) those people in whom lack of IgA in the blood would not have come to notice had they not had an immunoglobulin test for some other reason. Such people are entirely healthy, probably throughout their lives, as compensatory mechanisms make up for the lack of IgA, and (b) individuals in whom the IgA deficiency is a marker of other, more subtle, irregularities of their immune system. Some of these individuals suffer from recurrent infections, often affecting the sinuses or ears. Others suffer from allergies, and yet others make antibodies against themselves, a condition known as "autoimmunity".

What does this mean in practice?
Those IgA deficiency individuals who get recurrent infections may do so because they fail to make particular types of antibodies or are also missing a small proportion of IgG antibodies, such as one of the IgG subclasses. Nowadays immunological investigations can detect these subtle deficiencies and these tests should be carried out in specialist immunology centres in all patients with IgA deficiency and recurrent infections.

Patients with IgA deficiency who experience recurrent infections, and who are subsequently shown to have an additional IgG subclass or specific antibody deficiency, can benefit from IgG replacement therapy. Such patients require prompt antibiotic treatment on developing an infection as well.

Most IgA deficient patients make some IgA even if a very reduced level, but rarely it may be absent or virtually so. These individuals may make antibodies to the IgA if given a blood transfusion or other blood product, for any reason. This may be a cause of a "reaction" in future blood transfusions. Hence patients with absolute IgA deficiency should be checked for the presence of such antibodies, and may require to carry a card or a medic-alert bracelet if they are positive, in case they need further transfusions.

In the main most patients with IgA deficiency who suffer with infections can be improved by careful management and communication between their immunologist and their general practitioner.

For General Practitioners:

The important principles of management are:

1. Awareness of possible complications.
2. Prompt treatment with antibiotics, especially for sinusitis, chest infections (including bronchitis) and diarrhoea.
3. Recurrent sinusitis in IgA deficient patients will be made worse by poor drainage of sinuses and an ENT opinion is often helpful to prevent further infections. Sprays such as Beconase may help to prevent further ENT surgery.
4. Iron deficiency anaemia is common if there have been gastrointestinal complications and iron tablets may be helpful.
5. Oral polio, or salmonella vaccines which are live, should not be given. These provoke an anti-IgA response which will be absent in these patients. The intramuscular (killed) polio or salmonella polysaccharide vaccine should be substituted.

Medical information published by the PiA is approved by our Medical Advisory Panel. However, it is intended for general guidance only, and should not be used in place of the personal consultation needed with your physician.