A case of 'smouldering' mastocytosis with high mast cell burden, monoclonal myeloid cells, and C-KIT mutation Asp-816-Val

Mastocytosis is a term used for a group of disorders characterized by abnor mal growth and accumulation of tissue mast cells (MC) in one or more organ systems. In patients with systemic mastocytosis (SM) the clinical course ma y be indolent or aggressive or even complicated by leukemic progression or an associated clonal hematologic non mast cell lineage disease (AHNMD). How ever, at first presentation (diagnosis) it may be difficult to define the c ategory of disease and the prognosis. We report on a 48-year-old female pat ient with SM with urticaria pigmentosa-like skin lesions and mediator-relat ed symptoms. She was found to have splenomegaly, a high infiltration grade (MC) in bone marrow biopsies (> 30%), mild anemia, and a high serum tryptas e level (> 500 ng/ml). In addition, she exhibited discrete histologic signs of myeloproliferation in the 'non-affected' marrow and monoclonal blood ce lls established by C-KIT 2468A --> T mutation (Asp-816-Val) -analysis and H UMARA assay. Despite these findings, however, the clinical course was stabl e over years and no AHNMD or organ impairment developed. Because of the 'in termediate' clinical signs and absence of progression to aggressive disease , we proposed the term 'smouldering mastocytosis'. (C) 2001 Elsevier Scienc e Ltd. All rights reserved.