Abstract
Mast cell activation syndromes (MCAS) represent a heterogeneous clinical entity caused by episodic and severe mast cell activation, including primary and secondary mast cell disorders (MCDs). The group of primary or clonal MCDs refers to systemic mastocytosis, other clonal MCAS and hereditary hypertryptasemia, while the secondary MCAS is characterized by normal mast cells (MCs) which are activated by external triggers, such as allergens or physical stimuli. Another category of MCAS is the idiopathic form, when no trigger or genetic mutation can be identified. Symptoms of mast cell activation are due to release of specific mediators and can be seen in many diseases, such as allergies, with localized or systemic clinical manifestations. Confirmation of MCAS is based on diagnostic criteria proposed by an international group of experts and the best available evidence in this field. It is generally accepted that the clinical picture of MCAS is non-specific and there are few available laboratory tools, making it difficult for clinicians to identify and confirm this entity. The diagnosis is established after exclusion of other possible clinical entities in most of the cases. Therefore, the actual diagnostic criteria of MCASs, some relevant clinical aspects and laboratory tools used in clinical practice were reviewed.