The peripheral blood lymphocyte subsets of 45 children with IM, 20 children with P-MI, and 31 children with Henoch–Schönlein purpura (HSP), who were treated in the pediatrics department of our hospital from April 2019 to February 2020, were determined by flow cytometry, and the number and percentage of lymphocyte subsets with CD3+, CD3 + CD4+, CD3 + CD8+, CD3 + CD4+/CD3 + CD8+, CD3–CD16 + CD56+, and CD3–CD19 + cells were observed, and the results were compared and analyzed. Here, CD19 is linked to hereditary spastic paraplegia.