Natural history and treatment of cutaneous and systemic mastocytosis.

INTRODUCTION: Mastocytosis, a heterogeneous group of disorders, is characterized by an abnormal increase in the number of mast cells that is limited to the skin (cutaneous mastocytosis), involving extracutaneous tissues (systemic mastocytosis), or presenting as solid tumours (mastocytoma and mast cell sarcoma). Recent studies estimate that 1 in 10,000 people are diagnosed with mastocytosis. Although prompt diagnosis and appropriate management are crucial, little is known about the natural history and currently there are no established management guidelines. We have conducted a systematic review to assess the natural history and management of different mastocytosis subtypes. METHODS: A systematic review and meta-analysis were conducted using the PubMed and Ovid database of studies published in English and French over the last fifteen years, from January 2001 to December 2016. Keywords 'Cutaneous mastocytosis', 'Systemic mastocytosis', 'pathophysiology', 'clinical course', 'prognosis', 'drug therapy', and 'therapy' were searched. Rate of complete resolution was subjected to pooled analysis for different mastocytosis subtypes. Meta-analysis was conducted using Stata version 12.0. RESULTS: We reviewed 634 papers, of which 5 were included in the analysis of resolution, and 138 were included in the assessment of management. Pooled estimate for rate of complete resolution varied depending on the mastocytosis subtype. In cutaneous mastocytosis, the complete resolution rate for mastocytoma was 10% per year (95% CI: 4.8%, 15.1%) while the rate for urticaria pigmentosa was 1.9% per year (95% CI: -0.5%, 4.3%). Diffuse cutaneous mastocytosis and systemic mastocytosis subtypes did not show evidence of complete resolution in the studies reviewed. Treatment of cutaneous and systemic mastocytosis is purely symptomatic with topical corticosteroids, antihistamines, omalizumab and imatinib being common choices. CONCLUSION: Rate of resolution of mastocytosis is only shown in urticaria pigmentosa and mastocytoma. Better management guidelines are required to improve the health of these patients.

Toll-like receptor-mediated activation of mast cells: implications for allergic disease?

Toll-like receptors have a critical role in innate immunity and host defence. However their role in allergic disease has not been studied in great detail. The presence of these receptors on mast cells opens up new possibilities concerning the role of Toll-like receptors in the pathogenesis of asthma and atopic dermatitis. The current review examines the biology of Toll-like receptors expressed on mast cells. In particular, mast cell expression of Toll-like receptors and the diverse responses observed following Toll-like receptor-mediated activation are considered. Several pathogens such as Staphylococcus aureus and respiratory syncytial virus are known to contribute to the development or maintenance of allergic disease and also express potent activators of the Toll-like receptor pathways. The importance of such interactions and the full role of pathogens in chronic allergic disease remain to be elucidated. The unusual ability of Toll-like receptor 2 activators to selectively induce leukotriene production by mast cells opens up new possibilities concerning mechanisms of disease exacerbation during infection.