Peripheral neuropathy in IgD myeloma. Cerebrospinal fluid paraprotein analysis in three cases

High resolution polyacrylamide gel isoelectric focusing (IEF), followed by direct immunofixation with anti-delta chains monospecific antibodies, were used to detect and identify IgD paraprotein in the cerebrospinal fluid (CSF) of 3 patients affected by IgD myeloma. Two of these patients presented a paraproteinemic neuropathy. Blood-brain barrier damage was investigated by means of CSF/serum albumin ratio. IgG index and CSF and serum IgD/albumin ratio were also evaluated. An intrathecal origin of the IgD paraprotein was excluded. The correlation between the presence of the paraprotein in the CSF and the possible neurological involvement was also examined.