How to identify patients with advanced SM and its subtypes
Because of the wide range of clinical manifestations of this disease, a diagnosis of advanced systemic mastocytosis (advanced SM) often begins with the following assessments1:
Serum tryptase level
Bone marrow (BM) biopsy for mast cell infiltration
KIT D816V mutational testing (including allelic burden)
Evaluation for organ damage (especially liver and spleen)
The associated haematological neoplasm is frequently a myeloid disease, such as an overlap myelodysplastic–myeloproliferative disorder, and often indicates multilineage involvement of KIT D816V2
Organ damage findings, also known as C-findings, include: 1. BM dysfunction manifested by one or more cytopenia(s) (absolute neutrophil count <1.0 x 109/L, haemoglobin <10 g/dL, or platelets <100 x 109/L, but no obvious non–mast cell hematopoietic malignancy. 2. Palpable hepatomegaly with impairment of liver function, ascites, and/or portal hypertension. 3. Skeletal involvement with large osteolytic lesions and/or pathological fractures. 4. Palpable splenomegaly with hypersplenism. 5. Malabsorption with weight loss due to gastrointestinal (GI) mast cell infiltrates.1
ASM, aggressive systemic mastocytosis; MCL, mast cell leukaemia; SM-AHN, systemic mastocytosis with an associated haematological neoplasm.
References: 1. Pardanani A. Systemic mastocytosis in adults: 2017 update on diagnosis, risk stratification and management. Am J Hematol. 2016;91(11):1146-1159. 2. Gotlib J, Kluin-Nelemans HC, George TI, et al. Efficacy and safety of midostaurin in advanced systemic mastocytosis. N Engl J Med. 2016;374(26):2530-2541.