Background. Systemic mastocytosis is a heterogeneous group of rare hematological disorders those are characterized by neoplastic mast cell accumulation in extracutaneous organs with or without evidence of skin involvement. Diagnostics of systemic mastocytosis consist of the histological and cytological examination of bone marrow cells, immuno-histochemical or flow cytometric analysis of mast cell immunophenotype (aberrant CD2 and / or CD25 markers expression), serum tryptase measurement and detection of KIT D816V mutation.
Clinical presentation. 62 year old man was referred to the Vilnius University Hospital Santariskiu Klinikos because of intense back pain. Lumbar X-Ray changes were differentiated between osseous metastases and multiple myeloma. Both of these diseases have been ruled out after serum protein electrophoresis and instrumental examination. Histologic analysis of bone marrow trephine biopsy revealed deposition of mast cells and the diagnosis of systemic mastocytosis was es -tablished. The patient was treated with alpha- interferon. Since the multicolor FC assay has been introduced in Vilnius University Hospital Santariskiu Klinikos, patient's bone marrow sample was ana-ysed by this method. 0.012% of bone marrow cells comprised mast cells with aberrant CD2+dim CD25+ phenotype. In 2013, flow cytometry was repeated and 0.017% of aberrant mast cells were detected.
Conclusion. Systemic mastocytosis is a disease that requires a comprehensive and integrated diagnostics. The major WHO criterion of systemic mastocytosis - bone marrow infiltration by mast cells. The mat or WHO criterion of SM is multifocal infiltrates of mast cells in bone marrow. Nevertheless, bone marrow biopsy can show insufficient results those are needed to confirm SM. Theret fore, minor criteria play a very important role.
Flow cytometry is a rapid, sensitive and reliable method to assess the phenotype of mast cells, because a large number of cells is analysed, 8-10 cell parameters are detected simultaneously, normal and aberrant bone marrow mast cells can be compared and very low levels of mast cell can be identified while monitoring the disease.
Keywords: systemic mastocytosis, flow cytometry, aberrant phenotype, CD25, CD2.
