New developments in the field of mastocytosis and mast cell activation syndromes: a summary of the Annual Meeting of the European Competence Network on Mastocytosis (ECNM) 2019

Abstract

Mastocytosis are a group of hematologic neoplasms characterized by an accumulation of atypical mast cells in one or several organs/tissues, often accompanied by mast cell activation. Whereas in children the disease manifestations are mostly limited to the skin, in adults the disease is usually systemic (systemic mastocytosis; SM) and involves the bone marrow and/or other internal organs. Several variants of SM have been defined. Whereas most patients have indolent SM, some patients have advanced SM, which underlines the complexity of SM. In 2002, a European consortium of clinicians and scientists initiated a multidisciplinary, multi-national cooperative network, termed the 'European Competence Network on Mastocytosis' (ECNM), with the aim to improve diagnosis and therapy of patients with mastocytosis and other mast cell activation disorders. Since then, members of the ECNM have organized Annual Meetings in several European countries. The present article provides a summary of advances in the field presented during the 17th Annual ECNM meeting held in Salzburg in October 2019.

Keywords: KIT; Mast cell activation; classification; mastocytosis; scoring; tyrosine-kinase inhibitors.

Figure 1

Updated diagnostic algorithm for patients with a suspected mast cell activation syndrome (MCAS). After the patient has been clinically stabilized, the physician examines potential etiologies and asks for MCAS criteria. If the symptoms are severe and episodic, the likelihood of MCAS is quite high. MCAS consensus criteria are then applied to confirm MC involvement. MCAS criteria can also be applied when the symptoms are less severe and/or atypical. However, in most of these patients, MCAS criteria are not fulfilled. In a next step, the underlying etiology is examined. At this step of the workup, it is important to screen for multiple underlying disorders, since in patients with MCAS, more than one such underlying disease may be present (e.g. mastocytosis and allergy). Regarding mastocytosis, clinical indicators are typical skin lesions, a persistently elevated serum tryptase level and detection of the KIT D816V mutant in peripheral blood cells. According to the underlying condition, MCAS is classified into primary (clonal or genetic) MCAS, secondary MCAS (IgE-dependent allergen or non-IgE-dependent trigger), and idiopathic MCAS. In patients with clonal MCAS, the final diagnosis may be CM, SM, or monoclonal MCAS defined by 2 (but not more) minor SM criteria. In a final step, the management plan is established. CM: cutaneous mastocytosis; HαT: hereditary alpha-tryptasemia; MC: mast cell; MCA: mast cell activation; MMAS: Monoclonal/primary MCAS; SM: systemic mastocytosis. Adapted from Valent et al. [4].