Dacrocytes, or teardrop cells, are red blood cells that have adopted a distinct, pear-like shape with one rounded end and one tapered tail. Their presence on a peripheral blood smear suggests an underlying issue, signaling stress on the body’s red cell production or filtering machinery. However, dacrocytes do not automatically confirm a severe disease; their significance depends entirely on the number present and the clinical context. They can also appear due to transient causes or technical errors.
The Physical Mechanism of Teardrop Cell Formation
The characteristic shape of a dacrocyte results from mechanical stress applied to the red blood cell membrane in two distinct anatomical locations. One primary mechanism involves the bone marrow, the body’s factory for blood production. In conditions where the marrow is infiltrated by fibrosis, cancer cells, or other abnormal tissue, the normal architecture is distorted, leading to a crowded environment known as myelophthisis. As newly formed red cells attempt to exit this dense, fibrous tissue and enter the bloodstream, they are physically squeezed and stretched, permanently deforming into a teardrop shape.
The second major mechanism of deformation occurs in the spleen, which acts as a quality control filter for red blood cells. Red cells containing abnormal inclusions, such as remnants of DNA or precipitated hemoglobin, are subjected to “pitting” as they pass through the spleen’s narrow sinusoids. The spleen attempts to remove these inclusions, stretching the red cell membrane too far for it to snap back to its normal biconcave disc shape. This remodeling process leaves the cell with a pointed projection, often contributing to the dacrocytes seen in the circulation.
Hematological Conditions Primarily Associated with Dacrocytes
The most concerning context for dacrocytes is their association with severe hematological disorders, particularly those affecting the bone marrow structure. The most prominent disease linked to high numbers of teardrop cells is Primary Myelofibrosis (PMF), a chronic cancer where the bone marrow is progressively replaced by scar tissue. The extensive marrow fibrosis in PMF forces red cell production to shift to other organs, such as the spleen and liver, a process called extramedullary hematopoiesis. The mechanical stress endured by these cells as they are squeezed out of the fibrotic marrow and the filtering by an enlarged spleen creates the signature dacrocytes.
Dacrocytes also frequently appear in severe nutritional anemias, such as Megaloblastic Anemia caused by a deficiency in Vitamin B12 or folate. In this condition, red cell precursors in the marrow develop abnormally large sizes and fragile membranes due to impaired DNA synthesis. These oversized, structurally weak cells are more susceptible to deformation and fragmentation as they navigate the microvasculature, resulting in a population of dacrocytes.
Dacrocytes are also seen in severe Iron Deficiency Anemia, where red blood cells are abnormally small and contain insufficient hemoglobin. The lack of iron impairs the cells’ ability to maintain their shape and structural integrity, making them prone to mechanical distortion as they circulate. This population of microcytic, hypochromic cells often includes dacrocytes. Similarly, in Thalassemia Syndromes, which involve genetic defects in hemoglobin production, the structurally unsound red cells are easily damaged and can be filtered by the spleen into the teardrop configuration.
Situations Where Dacrocytes Are Not Pathologically Significant
Despite their strong association with severe disease, the presence of isolated dacrocytes is not always a sign of major pathology. The most common non-disease cause is a technical artifact that occurs during the preparation of the peripheral blood smear slide. If the blood is spread unevenly or too forcefully across the glass slide, the mechanical shearing action can stretch the red cells into a teardrop shape.
Laboratory professionals can often distinguish true dacrocytes from artifacts because artifactual cells tend to have sharply pointed ends and all point in the same direction, following the line of the slide-making force. In contrast, dacrocytes resulting from disease have blunter tips and point in random, haphazard directions.
Dacrocytes can also be related to a history of splenic dysfunction or removal. Since the spleen is a primary site of red cell remodeling, patients who have undergone a splenectomy or whose spleen is not functioning correctly may have varied red cell shapes, including dacrocytes, because the body’s main filtering mechanism is absent. In these individuals, the finding is expected and does not suggest a new, progressive marrow disorder.