Janeway Type 3:  also known as IgA deficiency:  is the most common immunoglobulin deficiency.  The major immunoglobulin in human saliva, nasal and bronchial fluids, and intestinal secretions, IgA guards against bacterial and viral reinfections.  Ultimately, IgA deficiency leads to chronic sinopulmonary (related to the paranasal sinuses and the airway of the lungs)  infections, GI diseases, and other disorders. 

Causes:  IgA deficiency seems to be linked to autosomal dominant or recessive inheritance.  The presence of normal numbers of peripheral blood lymphocytes carrying IgA receptors and of normal amounts of other immunoglobulins suggests that B cells may not be secreting IgA.  In an occasional patient, T-suppressor cells appear to inhibit IgA.  IgA deficiency is also link to  autoimmune disorders, since many patients with rheumatoid arthritis or SLE ( systemic lupus erythematosus) are also IgA deficient.  Some medications, such as anticonvulsants, may cause transient IgA deficiency.

Symptoms:

May have the following signs and symptoms-

Chronic sinopulmonary 

Respiratory allergy (often triggered by infection

GI tract diseases, such as celiac disease, ulcerative colitis, and regional enteritis

Autoimmune diseases, such as rheumatoid arthritis, SLE, hemolytic anemia, and chronic hepatitis

Malignant tumors, such as squamous cell carcinoma of the lungs, reticulum cell sarcoma, and thymoma

Some IgA deficient patients have no symptoms, possibly because they have extra amounts of low-molecular-weight IgM, which takes over IgA function and helps maintain immunologic defenses.

Diagnostic test:

Immunologic analyses of IgA deficient patients show serum IgA levels below 5 mg/dl.  Although IgA is usually absent from secretions in IgA deficient patients, levels may be normal in rare cases.

Test may also indicate auto antibodies and antibodies against IgG (rheumatoid factor).

Treatment:

Selective IgA deficiency has no known cure.  Treatment aims to control symptoms of associated diseases.