Monitoring of multiple sclerosis (MS) requires additional molecular markers. Recently, we used original TCA-precipitation/extraction approach in combination with MALDI TOF/TOF mass-spectrometry and identified earlier unknown 48 kDa form of the unconventional myosin IC isoform b (Myo1C) in blood serum of the MS patients. Further examination of TCA-extracted fraction of blood serum of these patients by means of thin-layer chromatography and HPLC gel-filtration allowed detecting 300-500 Da peptides. MALDI TOF/TOF massspectrometry of these peptides showed that they contain Ser-Pro-Cys amino acid sequence. We discussed potential mechanisms of a release of these peptides that were earlier unknown in blood serum of the MS patients.