Bone fragility in mastocytosis: Clinical insights from a 5-patient retrospective case series.

Objective: This retrospective case series aimed to describe 36-month skeletal, biochemical, safety, and patient-reported outcomes in five postmenopausal women with mastocytosis treated with denosumab. Methods: Atechnical expert panel (TEP) retrospectively evaluated five consecutive eligible patients with osteoporosis associated with indolent systemic mastocytosis. All subjects underwent physiatric assessment, DXA assessment, and Mini- Osteoporosis Quality of Life (Mini-OQoL) evaluation using the validated Italian version of the questionnaire. Data collected at baseline (T0), 18 months (T1), and 36 months (T2) following initiation of denosumab 60 mgevery 6 months, combined with cholecalciferol and calcium supplementation according to individual requirements, were descriptively analyzed. Results: Over 36 months, femoral and lumbar spine T-scores showed modest improvement/stabilization. Mean femoral T-score improved from −3.9 ±0.3 at baseline to −3.5±0.3 at 36 months, while lumbar spine T-score improved from −4.3 ±0.5 SD to −3.9 ±0.4. Vitamin D levels normalized during follow-up, and Mini-OQoL scores improved from 54.2±9 to 67.3 ±6. However, BMD remained within the osteoporotic range and one vertebral fracture was documented at 36 months. No severe adverse events were recorded. Conclusions: In this case series, denosumab was associated with stabilization or modest improvement of BMD and improvement in patient-reported quality of life over 36 months in women with osteoporosis secondary to indolent systemic mastocytosis. These preliminary observations should be interpreted cautiously because of the small sample size, lack of a comparator, and occurrence of one new vertebral fracture during follow-up. Thus, larger multicenter prospective studies are required.