Page 789 - Hematology_ Basic Principles and Practice ( PDFDrive )

C H A P T E R 48

NEUTROPHILIC LEUKOCYTOSIS, NEUTROPENIA, MONOCYTOSIS,

AND MONOCYTOPENIA

Lawrence Rice and Moonjung Jung

Abnormalities of leukocyte number are commonly encountered in infection or is at least a sign of illness severe enough to warrant
medical practice. The clinical significance of leukocytosis or leukope- hospital admission rather than outpatient management. Leukocytosis
nia varies from none at all to being an early clue to a life-threatening can also be a prominent presenting feature of leukemias and myelo-
process, whether a primary hematologic or secondary reactive process. proliferative neoplasms (MPNs). The presence of increased neutro-
Potential causes of leukocytosis or leukopenia are myriad. This phils assures that acute leukemia is not present. When leukocytosis
chapter considers disorders faced by adult practitioners in hospital is extreme, it indicates chronic myeloid leukemia (CML), other
and outpatient clinics where the predominant hematologic abnormal- MPNs, or a leukemoid reaction.
ity is neutrophilic leukocytosis, neutropenia, monocytosis, or mono- Leukemoid reaction has been defined as a reactive (nonclonal)
3
cytopenia; other chapters consider lymphocytosis, lymphopenia, neutrophilic leukocytosis with WBC count above 50,000/mm . This
eosinophilia, pancytopenia, and hematologic neoplasms. must be differentiated from a neoplastic proliferation.
The normal range for leukocyte count in most laboratories is from Leukoerythroblastosis refers to the presence in the peripheral blood
3
3
about 4500/mm to 11,000/mm . Neutrophils (and band forms) of immature myeloid cells (generally myelocytes) and nucleated
3
comprise the majority of circulating leukocytes (1800 mm to 7700/ RBCs, often with giant platelets as well. This is always abnormal.
3
mm ); monocytes are about 4% of cells (mean absolute count: 300/ Patients with leukoerythroblastosis do not necessarily have leukocy-
3
mm ). The physician must always think in terms of absolute counts tosis, but they usually do. Most patients (two-thirds) with leukoeryth-
of leukocyte subpopulations (total leukocyte count multiplied by the roblastosis have an underlying myelophthisic process, such as primary
differential percentage). Thus, in a patient presenting with a normal or secondary myelofibrosis, metastatic tumor, necrosis, or granulomas
3
white blood cell (WBC) count of 5000/mm and an elevated lym- in the bone marrow (BM). Therefore, BM examination is indicated
phocyte percentage of 65%, the differential diagnosis to be considered when leukoerythroblastosis is unexplained. Teardrop poikilocytes and
is that of neutropenia, not lymphocytosis, because the absolute elliptocytes on blood smear would strengthen concerns for myelo-
neutrophil count (ANC) is decreased but absolute lymphocytes are phthisis. In 20% of patients with leukoerythroblastosis, the cause is
normal (only relatively increased). hemolytic anemia, and miscellaneous other causes consist mainly of
When approaching a patient with abnormal leukocyte number, those with shock (septic, hemorrhagic, cardiogenic, anaphylactic)
several factors impact heavily on the differential diagnosis and the when hypoperfusion of areas of BM disrupt the microenvironment
vigor with which diagnosis and therapy should be pursued. Diag- and permit disorderly egress of precursor cells.
nostic considerations are vastly different when the abnormality first Left-shifted neutrophils refer to relative immaturity of circulating
manifests in the hospital versus in the outpatient clinic. Also cells, often manifest as an increased percentage of band neutrophils.
crucial is the degree of the abnormality, providing guidance to Marked left-shift includes less mature precursor forms, myelocytes
its likely cause and consequence. For example, agranulocytosis is a and metamyelocytes. Left-shift is nonspecific and may occur with
life-threatening disorder in which neutrophils are at or near zero, infection or any cause of marked neutrophilia.
has a limited spectrum of underlying causes (drug reactions being Detailed directed history and physical examination are indispens-
paramount), and demands immediate interventions. Duration has able to the evaluation of neutrophilia (Table 48.1). Fever and chills
major implications; determining the onset of changes and whether suggest infection (or inflammation), mandating a search for more
they are stable or progressive informs as to etiology and significance. specific symptoms that could pinpoint the focus. Examples include
Whether the abnormality is symptomatic—for example, whether a sore throat, pharyngeal erythema, and exudate in pharyngitis;
a neutropenic or monocytopenic patient has or has had infectious productive cough and abnormal lung auscultation in pneumonia; and
complications—bears on likely etiologies and need for therapy. dysuria and flank tenderness in urinary tract infection. Medication
If there are known or suspected comorbid conditions, such as history mainly explores glucocorticoid use. With mild chronic neu-
autoimmune or inflammatory disorders, this can crystallize the trophilia, smoking habits and obesity become considerations. Recent
approach; occasionally, the leukocyte abnormality may be the first vigorous exercise, emotional stress, burns, shock, or trauma can
sign of a previously unrecognized disorder or may provide important increase circulating neutrophils because of catecholamine-induced
confirmation (e.g., neutropenia in a patient with systemic lupus demargination. A positive family history may suggest hereditary
erythematosus [SLE]). If the leukocyte abnormality is accompanied neutrophilia. Often neglected are attempts to delineate the time
by additional hematologic abnormalities (unexplained abnormali- course of the leukocyte abnormality by seeking prior medical contacts
ties of red blood cells [RBCs], platelets, or cell morphology), this and blood count results at the time. On the physical examination,
would point away from disorders considered in this chapter and care should be directed to lymph node palpation because this can be
often toward a primary hematologic disease. Beyond history and an important clue for infection or malignancy. Palpable splenomegaly
physical examination, the peripheral blood smear is key to establish may not only direct the evaluation toward hematologic disorders but
the direction of further evaluation. can be a cardinal sign of a variety of infectious and inflammatory
disorders.
Blood smear should always be a part of initial evaluation when
NEUTROPHILIC LEUKOCYTOSIS (NEUTROPHILIA) there are abnormalities of blood counts. BM aspirate or biopsy
morphology may be helpful when pathophysiology and diagnosis are
A high WBC count, particularly a high neutrophil count, is common unclear. When appropriate, essential information can be gained by
with any infectious or inflammatory disorder. In the emergency sending BM for microbiologic cultures, cytogenetic or molecular, or
department, leukocytosis is often equated with significant bacterial other ancillary studies.

675