Systemic mastocytosis is a rare disease characterized by the uncontrolled clonal proliferation of abnormal mast cells in one or more extracutaneous organs. It is no longer considered a myeloproliferative neoplasia but a distinct subgroup following the review of the classification by WHO in 2016. The average age at diagnosis is 60 years regardless of gender. Bone involvement, in the broad sense, is very common and often asymptomatic. Osteoporosis or bone fragility concerns approximately 20 % of cases. The particularity of bone damage directly induced by mast cell proliferation is its heterogeneity, sometimes combining osteolysis and osteosclerosis simultaneously. This makes the interpretation of paraclinical values (bone density, biomarkers) complex and the therapeutic attitude becomes a real challenge.