This disease refers to serum IgA levels below 0.05 g/L, while IgG and IgM levels remain normal; it is the most common type of immunodeficiency. The prevalence in the population is approximately 1/700. Most cases are sporadic, with some being familial and affecting multiple generations. Epidemiological surveys of six ethnic groups in different regions of China indicate ethnic and regional variations in the disease. Abnormalities in the structural genes encoding the α heavy chain may not be the primary disease cause; the stagnation of IgA-producing B-cell maturation during early B-cell differentiation or the activation of IgA-specific suppressor T cells, leading to blocked B-cell maturation, may be the pathogenic mechanism.

bubble_chart Clinical Manifestations

Most patients are asymptomatic and are occasionally discovered during examinations. Other cases often present with varying degrees of sinus and respiratory infections; if bronchial asthma occurs, it is generally more severe. Some patients experience gastrointestinal symptoms, such as chronic diarrhea, malabsorption syndrome, and intestinal villous atrophy. Infection with Giardia lamblia is uncommon. Due to the lack of IgA secretion in the gastrointestinal and respiratory tracts, allergic reactions are more likely to occur. Additionally, there is an increased incidence of autoimmune diseases such as rheumatoid arthritis, systemic lupus erythematosus, thyroiditis, and pernicious anemia.

bubble_chart Auxiliary Examination

Serum and exocrine IgA levels are significantly reduced; a few patients also show decreased IgE and IgG₂. Since IgG₂ can produce more antibodies against certain polysaccharide antigens, these patients are prone to recurrent sinus and lung infections, which may even lead to obstructive lung disease. However, the number of circulating IgA-producing B cells is not low. When patients with this condition are exposed to plasma IgA or gamma globulin, they may produce anti-IgA antibodies, leading to allergic reactions upon subsequent blood transfusions or exposure to globulins. Additionally, these patients may produce antibodies against thyroglobulin, gastric parietal cells, smooth muscle, collagen, and food antigens. The positivity rate for anti-bovine serum albumin antibodies is also increased. If bovine antiserum is used to detect IgA, it may mask IgA deficiency. Therefore, it is more reliable to use other antisera (e.g., rabbit) for measurement.

Most do not require treatment. If there are respiratory infections, gastrointestinal symptoms, allergic reactions, or autoimmune diseases, corresponding management should be undertaken. Gamma globulin preparations contain only trace amounts of IgA, so they cannot selectively replace IgA; additionally, IgA is produced locally at mucosal surfaces, and systemic administration of IgA may not reach the intended sites of action, while repeated infusions are prone to allergic reactions. Therefore, gamma globulin is generally not used for treatment. It is only effective in cases of severe infection accompanied by IgG₂ deficiency when such preparations are applied. A minority of IgA deficiency cases may resolve spontaneously.