PART I NON-NEOPLASTIC HEMATOLOGY COPYRIGHTED MATERIAL CHAPTER ONE NON-NEOPLASTIC DISORDERS OF WHITE BLOOD CELLS Rebecca A. Levy, Vandita P. Johari, and Liron Pantanowitz OVERVIEW OF WBC PRODUCTION Leukocytes AND FUNCTION Hematopoeisis Hematopoiesis occurs in different parts of the Frequently the first test that suggests an imbalance or body, depending on the age of the embryo, child, or disturbance in hematopoiesis is the complete blood adult. Initially blood cell formation of the embryo count (CBC). The CBC is a simple blood test that occurs within the yolk sac, in blood cell aggregates is ordered frequently. It may pick up incidental called blood islands. As development progresses, abnormalities or may yield a diagnosis of suspected the hematopoiesis location changes, and the spleen abnormalities. The CBC is a count of multiple blood and liver become the primary sites. As bone marrow components and qualities, and can include a differ- develops, it usurps the task of blood cell formation ential of the white blood cells (WBCs). The CBC can and becomes the site for trilineage hematopoiesis. suggest infection, inflammatory processes, and malig- The bone marrow contains pluripotent stem cells, nant processes. Typically a peripheral blood smear which can develop into any of the blood cells, includ- and rarely a buffy coat (concentrated white blood ing granulocytes, monocytes, and lymphocytes, in cells) are analyzed to help determine a diagnosis response to specific stimulating factors (Andrews, (Efrati, 1960). A differential WBC assigns leukocytes 1994). Several white blood cells (leukocytes) are to their specific categories as a percentage or absolute depicted in Figure 1.1. Maturation, activation, and count. Manual differential counts tend to be accu- some proliferation of lymphoid cells occur in sec- rate but imprecise, whereas automated counts are ondary lymphoid organs, including the spleen, liver, fairly precise but sometimes inaccurate (Bain, 2002). and lymph nodes. Extramedullary hematopoiesis can It may occasionally be necessary to evaluate both take place in the liver, thymus, and spleen and may the bone marrow and blood smear to evaluate the lead to organomegaly. There is a common myeloid quality and quantity of the blood lineages. WBC progenitor cell called the CFU-GEMM (Colony- disorders are classified into quantitative and quali- Forming Unit-Granulocyte–Erythroid-Macrophage- tative conditions, reflecting changes in their number Megakaryocyte) that leads to the develop- and function, respectively (Stiene-Martin, 1998). This ment of granulocytic, monocytic, eosinophilic, chapter discusses both nonneoplastic quantitative basophilic, erythrocytic, and megakaryocytic and qualitative disorders of WBCs. precursors. Non-Neoplastic Hematopathology and Infections, First Edition. Edited by Hernani D. Cualing, Parul Bhargava, and Ramon L. Sandin. © 2012 Wiley-Blackwell. Published 2012 by John Wiley & Sons, Inc. 3 4 | CHAPTER ONE | Non-Neoplastic Disorders of White Blood Cells Band neutrophil Basophil Monocyte RBC 5–7 μm Neutrophil Eosinophil Mature lymphocyte FIGURE 1.1 Schematic drawings of different white blood cells shown in relation to an erythrocyte. The band neutrophil (10–18 μm) is characterized by a deeply indented nucleus and secondary granules. The segmented neutrophil (10–15 μm) has 2 to 5 nuclear lobes (4 depicted) connected by thin filaments and contains several cytoplasmic secondary (specific) granules. The basophil (10–15 μm) contains a segmented nucleus and many coarse, dense granules of varying size (that may obscure the nucleus). The eosinophil (10–15 μm) has a bilobed nucleus and cytoplasm filled with coarse, uniform granules. The monocyte (12–20 μm) has an indented nucleus and abundant gray cytoplasm with sparse granules. The presence of nucleoli indicates that this is an immature monocyte (promonocyte). The mature lymphocyte (7–15 μm) has a high nuclear:cytoplasmic ratio (4:1), slightly notched nucleus with dense clumpy chromatin and no nucleolus, and only moderate agranular cytoplasm. Leukocytosis Leukocytosis is defined as a total WBC count that is greater than two standard deviations above the mean, or a value >11,000/μL in adults. While leukocytosis is mainly due to a neutrophilia, it may reflect an increase in any of the other leukocytes. Patients with hyperleukocytosis, which is defined as a white cell count (WCC) >100,000/μL, may man- ifest with hyperviscosity (or so-called symptomatic hyperleukocytosis). The development of symptoms of hyperviscosity syndrome are often correlated with the underlying cause (e.g., hyperproteinemia, erytho- cytosis, hyperleukocytosis, and thrombocytosis) and is a medical emergency mainly seen with leukemia in blast crisis. The severity of hyperleukocytosis is related to the underlying disorder; hyperviscos- FIGURE 1.2 Leukemoid reaction observed in a peripheral ity is typically evident in AML with a WCC of blood smear. Notice the significant increase in early neu- >100,100/μL, in ALL with a WCC of >250,000/μL, trophil precursors and band forms in addition to segmented and in CLL with a WCC of 500, 000/μL (Adams, 2009; neutrophils. Rampling, 2003). Spurious leukocytosis can occur because of platelet clumping, increased nucleated syndrome may have transient leukemoid reactions erythrocytes, or in cryoglobulinemia (Savage, 1984; (Brodeur, 1980). Patel, 1987). Leukemoid Reaction Granulocytes Granulocytes have a single progenitor cell, the Leukemoid reaction is used to describe leukocytosis myeloblast, that can differentiate into neutrophils, above 50, 000/μL. This is usually characterized by eosinophils, and basophils (Lawrence, 1998). The a significant increase in early neutrophil precursors differentiation process is based on the presence of including band forms (Figure 1.2). Infants with Down certain stimulating factors. Neutrophils are the first Overview of WBC Production and Function | 5 responders to infection or inflammation, and they respond to cytokines such as interleukin-8 (IL-8), interferon gamma (IFN-gamma), and C5a (Witko- Sarsat, 2000). These chemicals direct the neutrophils migration to areas of need. Maturation Process Neutrophils undergo a maturation process as they shift from myeloblasts, to promyelocytes, to myelocytes, to bands; eventually they finish the mat- uration process as neutrophils which is depicted in Figure 1.3. Only bands and mature neutrophils are normally present in the peripheral blood smear. Other immature cells are very rarely detected in small numbers in the blood of healthy individuals (Oertel, 1998). Band neutrophils constitute about 10 FIGURE 1.4 Blood smear from a patient with infection to 15% of the nucleated cells in the bone marrow and showing a bandemia and a left shift. These band neu- around 5 to 10% of the nucleated cells in the periph- trophils all have nuclei that are indented to greater than eral blood (Glassy, 1998). The nucleus of a band is half the distance from the farthest nuclear margin. Their indented to greater than 50% of the diameter of the cytoplasm also contains many toxic granules. nucleus (i.e., horseshoe shaped). Eosinophils have the same maturation process; however, the cells are normally show leukocytosis and a leftward shift distinctively eosinophilic, with coarse eosinophilic (Christensen, 1979). Although the diagnostic value cytoplasmic granules. In this case the myeloblast of a left shift as an indicator for infection is lim- becomes an eosinophilic myelocyte that matures into ited (Seebach, 1997; Gombos, 1998), when the WBC an eosinophilic metamyelocyte, then an eosinophilic is low, bands may be the only clue of an infection. band, and ultimately an eosinophil. Basophils have a Occasionally band cell counts are requested to detect shorter transition from a myeloblast to a basophilic infection (e.g., in the neonate) (Bain, 2002). The pres- myelocyte and eventually a basophil. ence of a left shift and circulating nucleated red blood cells is referred to as a leukoerthyroblastic reaction Left Shift (or leukoerythroblastosis). There is often also asso- An increase (>20%) in the number of band cells (so- ciated erythrocyte anisopoikilocytosis (e.g., teardrop called bandemia) in relation to normal neutrophils cells or dacrocytes) with anemia and megakaryocyte is known as a left shift (Figure 1.4) (Nguyen, 2000). fragments in a leukoerythrobalstic pattern, indicative With a left shift the band count is usually >700/μL. of a space-occupying lesion within the marrow (i.e., When a left shift occurs, more immature granulocytes myelophthisic process). (blasts, promyelocytes, metamyelocytes, myelocytes) are typically released in the peripheral blood. Unless a Monocytes patient is receiving G-CSF therapy, circulating blasts Monocytes stem from monoblasts and undergo a are not normally seen in reactive conditions. In reac- maturation process as they progress from monoblasts tive neutrophilia the left shift contains mainly bands. to promonocytes. Monocytes reside in the peripheral A left shift may be physiological (e.g., pregnancy) or in blood. They may differentiate further and become response to infection, inflammation, shock, hypoxia, macrophages (sometimes referred to as histiocytes) or other marrow stimulation. Newborn infants may in the tissue. Myeloblast Promyelocyte Myelocyte Metamyelocyte Band Neutrophil FIGURE 1.3 Neutrophil maturation process. Neutrophils undergo a maturation process as they shift from myeloblasts, to promyelocytes, to myelocytes, to bands, and eventually to neutrophils. 6 | CHAPTER ONE | Non-Neoplastic