CST5 and systemic mastocytosis: Indeed, we considered this exploratory AP-MS study a starting point for further in-depth investigations designed to examine quantitative changes in the cystatin D-C26 interactome on a larger cohort of patients, on samples analyzed individually and not in a pool and with a comparison with other immunological diseases, with the aim of discovering novel candidate salivary biomarkers of systemic mastocytosis.