Likewise, we make a case for implementing TET2 mutational or expression profiling in AML patients with extramedullary disease, particularly with splenomegaly, given our data linking biallelic TET2 mutation with colonization of the spleen along with data from mouse models showing a proclivity of Tet2 mutation to drive extramedullary hematopoiesis and myeloid disease. The gene discussed is TET2; the disease is glycogen storage disease VI.