MRGPRX2 and Osteopenia: There was no link between the numbers of MRGPRX2+ cells, MRGPRX2-mRNA+ MCs, and CST+ and MBP+ cells in lesional skin of ISM patients and disease clinical characteristics, i.e., evidence of anaphylaxis and/or osteopenia/osteoporosis, severity of mastocytosis in the skin (MIS score), and symptom burden as assessed by MAS (Figure 4; Supplementary Figure 3).