Are Gastrointestinal Mucosal Mast Cells Increased in Patients With Systemic Mastocytosis?

Abstract

In patients with mastocytosis, gastrointestinal symptoms are a frequent phenomenon. However, there are only limited data about the quantity and distribution pattern of mast cells in the gastrointestinal mucosa. We stained gastroduodenal biopsy specimens from 27 patients with mastocytosis and 48 control subjects for mast cell tryptase, CD117, and CD25. The numbers of mucosal mast cells per high-power field showed wide variation in all groups and were decreased markedly in biopsy specimens of corpus and duodenum and statistically significantly decreased in antrum biopsy specimens from patients with systemic mastocytosis compared with patients with pure urticaria pigmentosa and with control subjects. Staining for tryptase showed highly significant correlation with staining for CD117. All mast cells were negative for CD25, which is expressed characteristically by neoplastic mast cells. Causes of the decrease of mucosal mast cells remain enigmatic, but our results show that gastrointestinal symptoms of patients with mastocytosis are most likely mediator-related and not due to an increase of local mast cells. The term mastocytosis comprises a heterogeneous group of diseases characterized by accumulation and abnormal growth of mast cells in various organs and tissues. If only the skin is affected, the disorder is termed urticaria pigmentosa (UP). If other organ systems such as the bone marrow, gastrointestinal tract, or spleen and lymph nodes are involved, the term systemic mastocytosis is used. According to the World Health Organization classification of 2001, the major criterion for the diagnosis of systemic mastocytosis is the evidence of dense infiltrates of mast cells, ie, aggregates of 15 or more mast cells, in 1 or more extracutaneous organs. 1 About 25% of patients with any kind of mast cell disease and 70% of patients with systemic mastocytosis show gastrointestinal symptoms, including abdominal discomfort, nausea, vomiting, and diarrhea, when a careful history is obtained. 2 However, there are only limited data on small patient groups about the quantity and distribution pattern of mast cells in the gastrointestinal tract. Therefore, we performed a quantitative analysis of mucosal mast cells in the stomach and duodenum using biopsy specimens from patients with pure UP or systemic mastocytosis (diagnosed by bone marrow involvement) with or without skin involvement and from control subjects.