KIT systemic mastocytosis associated with KIT acute erythroid leukaemia: first case report with molecular evidence for same progenitor cell derivation

Accepted 15 July 2009 Published Online First 2 September 2009 ABSTRACT A case of systemic mastocytosis associated with a clonal haematological non-mast cell lineage disease (SMAHNMD), where the associated disease is acute erythroid leukaemia (erythroid/myeloid type), is reported. Interestingly, molecular studies showed the KIT mutation not only in the mast cells, but also in the myeloid blast population and the leukaemic erythroid cells. As is the case with most erythroid leukaemias, the patient had a very aggressive clinical course and died shortly after diagnosis. It is believed that this is the first reported case of systemic mastocytosis with erythroid leukaemia where the KIT mutation was detected in all three cell types. Molecular findings provide evidence for derivation of these seemingly morphologically distinct lesions from the same clonal precursor cell. From a practice standpoint, this case illustrates the importance of definitively diagnosing the associated non-mast cell lineage disease due to its prognostic implications.