80 children with selective immunoglobulin A (IgA) deficiency-40 with severe deficiency (serum IgA 5 mg/dl but less than minus 2 SD of the age-normal mean)-were followed up for 1·5 to 9 years; during which their serum and salivary IgA levels were measured periodically and the number and type of infections they had were recorded. In the partial deficiency group serum IgA rose to normal levels in half the group at a median age of 14 years and at a median time of 4 years after diagnosis, but they did not reach the normal range in the severe deficiency group. Pneumonia occurred more frequently in the severe than in the partial deficiency group. In addition, 11 of the 12 severely IgA deficient patients who had pneumonia had levels of both serum and salivary IgA of less than 0·5 mg/dl, and only 1 had detectable serum IgA levels. These data indicate that in childhood severe IgA deficiency is persistent and predisposes to pneumonia, whereas partial IgA deficiency is often transient and only occasionally associated with pneumonia.
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