BTG3 and systemic mastocytosis: One patient had rheumatoid arthritis, one had IgG4-RD with positive anti-nuclear antibody (ANA) (AC-3 centromere 1:1,280), and one had systemic mastocytosis and polycythemia vera (systemic mastocytosis with an associated clonal hematological non-mast cell lineage disease) with JAK2V617F mutation and myelofibrosis.