Assessing real-world natural history of indolent systemic mastocytosis: A retrospective matched cohort study.

Background: Indolent systemic mastocytosis (ISM) is the most common form of systemic mastocytosis, accounting for more than 80% of cases. Patients with ISM experience severe, unpredictable symptoms, including potentially life-threatening anaphylaxis. As a chronic condition, understanding its longitudinal natural history is essential. Objective: We sought to evaluate the real-world disease burden and describe the natural history of ISM by comparing patients treated at Mayo Clinic to a matched control cohort. Innovative natural language processing methods were used alongside traditional structured data analysis. Methods: A retrospective cohort study was conducted using data from patients diagnosed with ISM at Mayo Clinic between January 1, 2005, and June 30, 2022. Patients were identified using structured electronic health record data and natural language processing of clinical notes. A control cohort was created using 10:1 propensity matching based on demographic and clinical variables. Baseline characteristics, symptoms, clinical outcomes, and health care utilization were assessed. Results: The study included 203 patients with ISM and 2030 matched controls. Patients with ISM had a higher symptom burden (mean, 7.4 vs 4.8 at baseline) and significantly more comorbidities. Bone involvement (osteopenia/osteoporosis) was present in 68% of patients with ISM versus 28% of controls ( Conclusions: Patients with ISM experience a high burden of heterogeneous symptoms and elevated rates of bone disease. These findings support the consideration of disease-modifying therapies in ISM management.