Reading below is the definition of Indolent Miastocytosis and the explanation of where the term smouldering originated.

Leuk Res. 2001 Jul;25(7):627-34.
A case of 'smouldering' mastocytosis with high mast cell burden, monoclonal myeloid cells, and C-KIT mutation Asp-816-Val.

Jordan JH, Fritsche-Polanz R, Sperr WR, Mitterbauer G, Födinger M, Schernthaner GH, Christian Bankl H, Gebhart W, Chott A, Lechner K, Valent P.

Department of Internal Medicine I, Division of Hematology and Hemostaseology, University of Vienna, Vienna, Austria.
Abstract

Mastocytosis is a term used for a group of disorders characterized by abnormal growth and accumulation of tissue mast cells (MC) in one or more organ systems. In patients with systemic mastocytosis (SM) the clinical course may be indolent or aggressive or even complicated by leukemic progression or an associated clonal hematologic non mast cell lineage disease (AHNMD). However, at first presentation (diagnosis) it may be difficult to define the category of disease and the prognosis. We report on a 48-year-old female patient with SM with urticaria pigmentosa-like skin lesions and mediator-related symptoms. She was found to have splenomegaly, a high infiltration grade (MC) in bone marrow biopsies (>30%), mild anemia, and a high serum tryptase level (>500 ng/ml). In addition, she exhibited discrete histologic signs of myeloproliferation in the 'non-affected' marrow and monoclonal blood cells established by C-KIT 2468A-->T mutation (Asp-816-Val) -analysis and HUMARA assay. Despite these findings, however, the clinical course was stable over years and no AHNMD or organ impairment developed. Because of the 'intermediate' clinical signs and absence of progression to aggressive disease, we proposed the term 'smouldering mastocytosis'.]

PMID: 11377687 [PubMed - indexed for MEDLINE]

http://www.ncbi.nlm.nih.gov/pubmed/11377687