Bone Mineral Content in Patients with Anaphylactic Reactions, Signs of Mastocytosis and Elevated Basal Serum Tryptase Levels

Introduction: To examine the relationship between elevated basal serum tryptase levels (BST), a marker of total mast cell mass, and bone mineral density (BMD) in patients with anaphylactic reactions and signs of mastocytosis. Methods: Retrospective evaluation of patient charts at an allergy unit. Patients with BST levels above 20 ng/ml were eligible if clinical and follow-up data and results of dual X-ray absorptiometry (DXA) were available. Patients with previous use of anti-osteoporotic medications and with osteoporosis not caused by mastocytosis were excluded. Spearman’s rank correlation, Mann-Whitney test and receiver operating characteristic curve (ROC) was used for analysis. Results: 24 patients were included. The main presenting symptom (17 of 24 patients) was anaphylactic reactions to insect stings. BST levels ranged between 21 and 158 ng/ml (median 48 ng/ml). Study participants with Z-score values below 1.0 had a median BST level of 46 ng/ml, the patients with Z-score values above or equal to -1.0 had a median BST level of 27 ng/ml. ROC analysis of the patient group with BST values between 30 and 100 ng/ml revealed a best cut-off value of BST to detect a low BMD when BST level would be at least 27 ng/ml resulting in a sensitivity of 92% and a specificity of 70%. Conclusion: Patients with moderately elevated BST levels seem to be at increased risk for low BMD.