Altered immunoglobulin concentrations and light chain ratios in juvenile onset mixed connective tissue disease.

Immunological disturbances may result in altered immunoglobulin concentrations and kappa/lambda light chain (kappa/lambda) ratios. We measured the kappa/lambda ratios of total serum immunoglobulins and of polyclonal IgG, A, and M separately as well as concentrations of these immunoglobulins in fourteen patients with juvenile onset mixed connective tissue disease. When comparing the patient group with a reference group the mean serum IgG and IgA concentrations were respectively 2.98 G/L (p = 0.0012) and 0.79 G/L (p = 0.0114) higher in the group of patients with juvenile onset mixed connective tissue disease. The mean IgM concentration was 0.39 G/L (p = 0.0002) lower. The mean kappa/lambda ratios of total serum immunoglobulins, serum IgG, and serum IgA were respectively 0.20 (p = 0.0226), 0.28 (p = 0.0016) and 0.10 (p = 0.0732), higher in the group of patients with mixed connective tissue disease as compared with the reference group. Mean serum IgM kappa/lambda ratio, however, was 0.21 (p = 0.0046) lower. The alterations of the serum immunoglobulin concentrations and of the kappa/lambda ratios reflect immunological disturbances in patients with juvenile onset mixed connective tissue disease. The increased concentration of serum IgG and raised IgG kappa/lambda ratio and decreased concentration of serum IgM with decreased IgM kappa/lambda ratio indicate that the synthesis of kappa-bearing immunoglobulins mainly is affected.