dacrocyte

**Definition:** Dacrocytes (Greek "dakryon" = tear) are RBCs with a single tapered tail or point, giving a teardrop or pear shape.

**Pathophysiology:** Two main mechanisms are proposed. (1) Deformed RBCs get stretched as they squeeze through fibrotic marrow or through the splenic cords and sinusoids. Splenic or marrow macrophages then pit out inclusions (e.g., Heinz bodies or precipitated globin chains), leaving the cell with a tail. (2) Abnormal erythropoiesis in a distorted marrow architecture produces misshapen cells that are released into the circulation.

**Key associations:** - **Primary myelofibrosis:** The classic association. The smear is leukoerythroblastic (teardrop cells, nucleated RBCs, immature granulocytes). Other findings include marrow fibrosis ("dry tap" on aspiration), JAK2 V617F mutation (~50–60%), CALR or MPL mutations, and massive splenomegaly from extramedullary hematopoiesis. - **Myelophthisic anemia:** Marrow replacement by metastatic cancer, granulomas (TB), or fibrosis. - **β-Thalassemia (major and intermedia):** Along with target cells, microcytosis, and basophilic stippling. - **Others:** Megaloblastic anemia, iron deficiency (less common), sideroblastic anemia, and hemolytic anemias.

**Clinical significance:** Teardrop cells are a clue to marrow infiltration or fibrosis. In a patient with anemia, splenomegaly, and a leukoerythroblastic smear, think myelofibrosis. Workup includes JAK2/CALR/MPL testing and bone marrow biopsy. Treatment options include JAK inhibitors (ruxolitinib) and allogeneic stem cell transplant.

**Boards pearl:** Teardrop cells plus a dry tap plus splenomegaly = myelofibrosis. Don't confuse them with schistocytes (fragmented RBCs seen in microangiopathic hemolytic anemia, e.g., DIC, TTP/HUS, mechanical valves) or spherocytes (hereditary spherocytosis, autoimmune hemolytic anemia).