Clinical Signs and Symptoms
Patients with clinical symptoms usually present with a history of frequent infections involving the respiratory tract such as otitis media (ear infection), sinusitis, bronchitis, or pneumonia. The causes of these infections are often found to be encapsulated (closed in a sheath) bacteria such as Hemophilus influenzae and Streptococcus pneumonia, especially in the case of an IgG2 deficiency. Lung function impairment and bronchiectasis (widening and scaring of airways) also have been reported in some patients. Some patients develop autoimmunity (immunity to the body's own tissues). Clinical presentation of these patients appears to vary according to the type of IgG Subclass deficiency which is present.
IgG2 deficient patients may have a poor response to some vaccines, such as the pneumococcal or the Hemophilus influenzae vaccines.
Since infants have little IgG at birth and the amount of IgG increases over the first few years of life to approach adult levels at about age 2, it is logical that the levels of the IgG subclass increase also. But this happens at a different rate for each child, thus, for infants and children, the "normal" range for IgG subclasses is very broad. A young child of one or two can have lower than normal levels of one or more IgG subclasses, but then later have entirely normal levels. IgG2 deficiency is the most common subclass deficiency in early childhood while IgG3 deficiency is the most common in adults.
While a deficiency of one subclass may be noted, this does not necessarily mean that a biologically important defect is present. What is important is that enough active binding antibody is found in the blood. This can be determined by measuring the levels of antibody to various vaccine agents (diphtheria, tetanus, measles, pneumococci, etc.) and by purposefully immunizing to determine how much response is made. Another issue is that IgG Subclass values may vary from laboratory to laboratory and deficiency of a given subclass may not correlate with clinical disease.
Various minor abnormalities of B- and T- lymphocyte level and function also have been reported.
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