Pencil cells and teardrop cells in microcytic hypochromic anemia
Pencil-shaped erythrocytes (elongated elliptocytes) with microcytic hypochromic anemia most commonly reflect iron deficiency anemia with anisopoikilocytosis. [1] Teardrop cells (dacrocytes) most commonly reflect bone marrow fibrosis or bone marrow infiltration, which can coexist with severe anemia or appear in selected anemias. [2]
Pencil-shaped (linear/elliptocytic) cells
Pencil cells are typically elongated elliptocytes that occur in iron deficiency anemia. [1] Pencil cells reflect heterogeneous red cell morphology caused by impaired and variably ineffective erythropoiesis in iron deficiency. [1]
Teardrop (dacrocyte) cells
Dacrocytes are teardrop-shaped poikilocytes that are classically associated with marrow fibrosis or myelophthisis states. [2] Infiltrative or fibrotic marrow processes create abnormal red cell transit through a distorted marrow environment. [2]
Overlap explanations in microcytic hypochromic anemia
Iron deficiency anemia can show anisopoikilocytosis with pencil cells on smear. [1] Teardrop cells may also be seen in iron deficiency anemia in some reports, although persistent or prominent teardrops should prompt evaluation for marrow fibrosis/infiltration. [2]
Differential diagnosis requiring confirmation
Primary myelofibrosis and other myelophthisic marrow conditions are common causes of dacrocytes. [2] β-thalassemia and megaloblastic anemia can be associated with dacrocytes, depending on the overall smear and indices pattern. [3]
Common pitfalls to avoid
Dacrocytes are not specific for a single cause and should not be attributed to iron deficiency alone when marrow fibrosis or infiltration is possible. [2] Attributing both pencil cells and teardrop cells to iron deficiency without considering marrow pathology can delay diagnosis of myelophthisic disorders. [2]
Practical interpretation approach
Assessment should integrate smear morphology with red cell indices and iron studies to support iron deficiency when microcytosis and hypochromia are present. [1] Assessment should include evaluation for marrow fibrosis or infiltration when teardrop cells are prominent or accompanied by other cytopenias or leukoerythroblastic changes. [2]
Summary of the most likely causes
Pencil-shaped linear cells are most likely due to iron deficiency anemia. [1] Teardrop cells are most likely due to bone marrow fibrosis or myelophthisic processes, with possible occurrence in selected anemias including iron deficiency or β-thalassemia. [2]