elliptocyte

**Definition:** Elliptocytes are RBCs with an elliptical (cigar/pencil-shaped) morphology, where the long axis is more than twice the short axis. Ovalocytes are egg-shaped, with a long axis less than twice the short axis. Both are often grouped together.

**Pathophysiology (Hereditary Elliptocytosis, HE):** - Autosomal dominant (most commonly) defects in RBC membrane cytoskeletal proteins: alpha-spectrin, beta-spectrin, protein 4.1 (and less commonly glycophorin C). - These defects impair horizontal interactions (spectrin dimer-dimer self-association) in the membrane skeleton, which weakens the membrane's ability to recover its shape after deformation in the circulation. The cells become elliptical over time as they pass through the microvasculature. - Abnormal cells are removed by the spleen (extravascular hemolysis).

**Clinical features of HE:** - Most patients are asymptomatic or have mild hemolysis. Some have a chronic hemolytic anemia with jaundice, splenomegaly, pigmented gallstones (bilirubin), and an increased risk of aplastic crisis with parvovirus B19. - Severe forms include hereditary pyropoikilocytosis (HPP), with fragmentation and budding of RBCs, and Southeast Asian ovalocytosis (SAO, band 3 mutation; stomatocytic ovalocytes, protective against malaria). - Labs: increased indirect bilirubin, increased LDH, decreased haptoglobin, increased reticulocytes. The Coombs test is negative. The osmotic fragility test is normal to increased. - Treatment: usually none. Folate supplementation. Splenectomy for severe hemolysis.

**Other causes of elliptocytes/ovalocytes (high-yield differential):** - Iron deficiency anemia: "pencil cells" (thin, elongated hypochromic elliptocytes), along with microcytosis and increased RDW. - Thalassemias: along with target cells, microcytosis, and hypochromia. - Megaloblastic anemia (B12/folate deficiency): macro-ovalocytes plus hypersegmented neutrophils. - Myelofibrosis: along with teardrop cells (dacrocytes) and leukoerythroblastic picture. - Myelodysplastic syndromes.

**Board tips:** - Elliptocytes + hemolysis + family history → hereditary elliptocytosis. - Don't confuse with hereditary spherocytosis (spherocytes, no central pallor, ankyrin/spectrin/band 3/protein 4.2 defects, increased MCHC, positive osmotic fragility/EMA binding test, Coombs negative). - Pencil cells on smear → think iron deficiency. - Macro-ovalocytes + hypersegmented neutrophils → think megaloblastic anemia.