DETECTION OF MI TRANSCRIPTION FACTOR (MITF) MESSENGER-RNA IN A CASE OF MYELODYSPLASTIC SYNDROME AND BONE-MARROW MASTOCYTOSIS

Myelodysplastic syndromes (MDS) may be accompanied by systemic mastocy tosis. The mechanisms which play a role in the evolution of mastocytos is, however, are not well understood. We report on a case of refractor y anemia with ringed sideroblasts (RARS), and co-existing bone marrow mastocytosis. Compact mast cell (MC) infiltrates were detected in bone marrow sections by immunohistochemistry using an antibody to tryptase . In addition, the MC were found to express c-kit, the tyrosine kinase receptor for MGF (mast cell growth factor = stem cell factor, SCF). A ctivating point mutations in the kinase domain of c-kit (often found i n mastocytosis) were not detectable. However, the mononuclear cells (M NC) of the bone marrow expressed mRNA specific for MITF, a transcripti on factor that regulates expression of c-kit and differentiation of MC . Surprisingly, the c-kit ligand SCF was found to augment expression o f MITF mRNA in bone marrow MNC. Whether this augmentation represents a general response (preventing loss of growth factor receptor expressio n during cell maturation) common to all types of hemopoietic progenito rs, or is confined to (some forms of) mastocytosis, remains unknown.