IgG paraproteinemias: a comparative CSF and serum study

In 10 neurologic patients routine isoelectric focusing of CSF and serum revealed monoclonal IgG paraproteinemia (3 multiple myelomas and 7 benign monoclonal gammopathies). Quantitative protein study showed blood-brain barrier damage in 7 out of 10 patients; 2 patients had intrathecal synthesis of IgG measurable by Reiber's formula. Each case showed identical monoclonal IgG pattern in CSF and serum at isoelectric focusing and immunofixation. We suppose that monoclonal IgG detectable in the CSF usually derive from the serum across the intact or damaged barrier. The occurrence of quantifiable intrathecally synthesized IgG in 2 patients, both with skeletal lesions close to the subarachnoid spaces, and the identical patterns of IgG in CSF and serum suggest that tumoral plasma cells secrete monoclonal IgG into blood and CSF from the bone location.