Functional SMN protein of peripheral blood-derived mononuclear cells was detected with an anti-SMN antibody labeled with a fluorescent dye and analyzed semiquantitatively using intracellular expression intensity and SMN spot formed in cell nucleus as an index, Consider the relationship with the clinical condition and motor function.Briefly,1) In order to identify the cell fraction, the fluorescently labeled cell surface antigen-specific antibody is added to the whole blood sample and stained.2) Hemolyze peripheral blood and fix mononuclear cells.3) Intracellular staining is performed with SMN protein and nuclear-specific fluorescently labeled antibody.4) SMN protein expression analysis was performed on a strongly CD33 cell population detected as a cell surface marker, SMN spot detection algorithm was used to analyze the proportion of cells in which intracellular SMN expression and SMN protein aggregated in the nucleus.