poikilocytosis

Poikilocytosis describes variation in RBC shape and is identified on peripheral blood smear review. Different poikilocyte morphologies correlate with specific diseases, making shape identification clinically useful:

- Schistocytes (fragmented cells, helmet cells): microangiopathic hemolytic anemia (TTP, HUS, DIC), mechanical heart valves - Spherocytes: hereditary spherocytosis, autoimmune hemolytic anemia - Sickle cells (drepanocytes): sickle cell disease/trait - Target cells (codocytes): thalassemia, liver disease, HbC disease, post-splenectomy - Teardrop cells (dacrocytes): myelofibrosis, myelophthisic processes, extramedullary hematopoiesis - Acanthocytes (spur cells): liver disease (abetalipoproteinemia), spur cell anemia - Echinocytes (burr cells): uremia, pyruvate kinase deficiency, artifact - Elliptocytes/ovalocytes: hereditary elliptocytosis - Bite cells: G6PD deficiency (after oxidative stress) - Stomatocytes: hereditary stomatocytosis, liver disease, alcoholism

Pathophysiologically, poikilocytosis results from membrane defects (structural protein abnormalities), oxidative damage, mechanical shearing stress, or abnormal hemoglobin polymerization, depending on the underlying cause. The RBC membrane's biconcave shape depends on cytoskeletal proteins (spectrin, ankyrin, band 3, protein 4.1); defects in these proteins alter cell shape and deformability, often leading to premature splenic destruction and hemolysis.

Clinically, identifying the specific poikilocyte type on smear narrows the differential diagnosis significantly and guides further workup (e.g., osmotic fragility test for spherocytosis, hemoglobin electrophoresis for sickle cell disease, ADAMTS13 activity for TTP). This is a classic integration point between pathology and clinical medicine on board exams.