Published Online: June 27, 2014
Indolent systemic mastocytosis (ISM) is defined by the presence of abnormal mast cells in the bone marrow. Mast cells produce and release a large number of different mediators, e.g. histamine, proinflammatory cytokines, chemokines and tryptase. Mast cell mediators are branded to have deleterious effects on bone metabolism. Fragility fractures, also known as low energy trauma fractures, and osteoporosis frequently occur in ISM patients, also before 50 years of age. Therefore, it is important for patients and physicians to recognize the risk for future fragility fractures as early as possible.
In an article recently published in The Journal of Allergy and Clinical Immunology (JACI), van der Veer and colleagues developed a prediction tool to identify individual ISM patients with a high risk of new fragility fractures. They used data of clinical, lifestyle, and bone characteristics collected from 221 ISM patients at time of diagnosis. After median follow-up of 5.4 years (range 0.4-15.3), data of lifetime fractures and trauma circumstances were collected from vertebral morphometry, and from patient records and questionnaires. Lifetime fractures were categorized a) in high versus low energy trauma circumstances and b) before and after ISM diagnosis. Subsequently, the authors analyzed which patient characteristics at time of diagnosis can predict the occurrence of new fragility fractures.
Lifetime fragility fractures were reported by 90 (41%) of the 221 ISM patients (aged 19-77 years), of these patients, 56 reported 125 new fragility fractures post-diagnosis. 15% of the patients only had high energy trauma fractures and 43% reported no fractures. The authors calculated a 10-year fragility fracture risk of 31±4%. A quarter of the patients who experienced new fragility fractures had osteoporosis at time of diagnosis, thus BMD alone does not have sufficient power to predict the risk of new fractures.
Male gender, high serum levels of the bone resorption marker CTX, low hip bone mineral density, absence of urticaria pigmentosa, and alcohol intake were identified as independent predictors of future fragility fractures in patients presenting with ISM. The sum of these five characteristics, each given 1 point, forms the MastFx-score and calculates the risk of an individual patient. The authors showed that ISM patients with a MastFx-score of ≥2 points have a high risk of fragility fractures. Additional analyses demonstrated that the MastFx-score is more useful than an existing fracture risk calculation tool developed for the general population aged between 30 and 99 years.
The authors concluded that calculation of the fragility fracture risk with the MastFx-score should be an important component in the management of patients presenting with ISM. The high occurrence of fragility fractures underlines the importance of optimizing bone quality in all ISM patients. Therefore, frequent exercise, adequate vitamin D and calcium intake, and alcohol cessation is highly recommended. High-risk patients will probably benefit from an early start of therapeutic intervention.
The Journal of Allergy and Clinical Immunology (JACI) is an official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.