sign in sign up
<<
Home , Basophilia, Left shift (medicine), Neutrophil, Neutrophilia, Toxic granulation

COMMON MORPHOLOGICAL ABNORMALITIES OF

Some of the more common abnormalities of neutrophil morphology that can be seen in peripheral are described below.7,12

1. PELGER–HUËT ANOMALY

Pelger–Huët anomaly is a rare benign autosomal dominant disorder characterized by defective nuclear segmentation (hypo-segmentation of the nucleus in (Figure 5). Nuclei are bi-lobed, dumbbell-shaped or do not have lobes at Figure 5A all. It is important to differentiate from the acquired hypo- segmentation of the neutrophil nucleus, also called pseudo- Pelger–Huët anomaly, which has been observed in , myelodysplastic syndromes, hematological malignancies and in patients on certain transplant or other drugs.

2. NEUTROPHIL NUCLEAR HYPER- SEGMENTATION

Figure 5B Neutrophil nuclear hypersegmentation is the presence of more than five nuclear lobes in the neutrophils (Figure 6). Figure 5. Pelger-Huët cells with The presence of hypersegmented neutrophils is a sensitive defective nuclear segmentation. A: Lack of nuclear lobes and specific sign of megaloblastic , associated with B: Bi-lobed nucleus vitamin B12 or folate deficiency. Less frequently, it can be seen in other disorders such as chronic , , iron deficiency, hypogonadism and chronic myelogenous .

3. DÖHLE BODIES

Döhle bodies are single or multiple blue or grayish-blue cytoplasmic inclusions, representing free or rough , usually situated at the periphery and Figure 6. Neutrophil protruding beyond the normal contour of the (Figure with hypersegmented nucleus. 7). They may be associated with myeloid left shifts, normal pregnancy, , various neoplasms and severe burns.

Figure 7. Döhle body in a segmented neutrophil.

Learning Guide: WBC: Neutrophil Granulocytes 7 4.

Toxic granulation refers to the presence of prominent purplish or blue-black granules (Figures 8 and 9) in the of segmented and band neutrophils in patients with severe infections and other inflammatory conditions. These granules are actually primary granules, normally dominating the cytoplasm of and early neutrophilic . Toxic granules are positive.

5. TOXIC VACUOLIZATION Figure 8. Segmented neutrophil with toxic granules. Toxic vacuolization is the presence of vacuoles in the cytoplasm of neutrophils in response to severe infections or inflammatory conditions (Figure 9). Vacuoles represent increased phagocytic activity and may suggest sepsis. Toxic vacuolization may be associated with toxic granulation and Döhle bodies. Vacuoles may also form as an artefact in neutrophils and in blood films if the smear is made after several hours of storage of the blood sample.

6. DYSPLASTIC/HYPOGRANULAR NEUTROPHILS Figure 9. Band neutrophil with The presence of dysplastic neutrophils is a characteristic feature cytoplasmic vacuolization and of myelodysplastic syndromes but has also been noticed in toxic granules. leukemoid reactions, multiple myeloma and drug sensitivity reactions. Morphologically, the normal synchronous maturation of nucleus and cytoplasm is lost. As a result, the primary and secondary granules in the cytoplasm are often decreased or absent, causing the cytoplasm to appear pale and bluish. The nucleus may show abnormal lobulation (hypo- or hypersegmentation or even ring forms). Figure 10 demonstrates an example of a peripheral smear from a patient with myelodysplastic syndrome, showing hypogranular cytoplasm and atypical nuclei in neutrophils.

Figure 10. Neutrophil granulocytes with hypogranular cytoplasm and atypical nuclear forms.

8 Learning Guide: WBC: Neutrophil Granulocytes QUANTITATIVE ABNORMALITIES OF NEUTROPHIL GRANULOCYTES

Neutrophils are the most abundant white type in human blood. They comprise approximately 40% to 70% of total circulating WBCs.

The count of neutrophils varies by age and shows other demographic differences. Table 1 shows example reference ranges by age in the healthy population.13

TABLE 1. EXPECTED RANGE OF NEUTROPHIL GRANULOCYTES IN HEALTHY INDIVIDUALS

NEUTROPHIL COUNT AGE % NEUTROPHIL (x 109/L)

At birth 5.0-22.2 55-74

6 months 1.5-7.3 25-40

4 years 1.5-9.2 35-50

Adult 1.8-7.7 40-85

*Laboratories are recommended to establish, or, at least, verify their own reference range.

NEUTROPENIA

Neutropenia is an abnormally low concentration of neutrophils in blood. Neutropenia may be selective or part of a general pancytopenia. When the absolute neutrophil level falls below 0.5 × 109/L tthe patient is susceptible to (sometimes recurrent or life threatening) infections.

Clinically, neutropenia is considered acute when it develops over hours to a few days, usually caused by rapid neutrophil use/destruction or else impaired production. Neutropenia is considered chronic when it lasts months to years, usually arising from reduced production or excessive splenic sequestration. Neutropenia may also arise from various disorders of function resulting in a decreased rate of release of neutrophils into the circulation. It is a common manifestation in several bone marrow failures, such as aplasia, leukemia or myelodysplasia.

Neutropenia can be caused by an intrinsic defect in bone marrow myeloid cells in congenital and idiopathic neutropenias, or by factors extrinsic to bone marrow resulting in acquired neutropenias.12 Acquired neutropenia can be due to decreased production or increased destruction. The majority of neutropenias is an acquired condition,7 with infections being the most common cause. Neutropenia is the most prevalent drug- induced blood dyscrasia. Neutropenia due to drugs can have different pathogenesis. Antifolate and other drugs result in neutropenia via direct suppression of the bone marrow. Non-chemotherapy (idiosyncratic) drug-induced neutropenia is due to increased (usually immune-mediated) neutrophil destruction.

Learning Guide: WBC: Neutrophil Granulocytes 9 The five drugs most frequently associated with idiosyncratic drug–induced neutropenia in a recent study were carbimazole, amoxicillin, cotrimoxazole, ticlopidine, and valganciclovir.14 Leukemic and tumor cells can also sometimes replace normal bone marrow elements, which can result in cytopenias, including neutropenia. Table 2 lists the causes of neutropenias.

TABLE 2. CAUSES OF NEUTROPENIAS

CAUSES OF CONGENITAL AND IDIOPATHIC CAUSES OF ACQUIRED NEUTROPENIAS NEUTROPENIAS

Severe congenital neutropenia (Kostmann’s disease) Neonatal alloimmune neutropenia

Autoimmune neutropenia (which is present in certain Reticular dysgenesis conditions, e.g., rheumatoid arthritis, systemic lupus erythematodes, scleroderma, etc.)

Neutropenia associated with viral infections (e.g., Familial benign chronic neutropenia hepatitis, HIV, etc.)

Chronic idiopathic neutropenia of adult (-mediated Neutropenia associated with fungal, rickettsial and syndrome) protozoal infections

Neutropenia associated with bacterial infections (e.g., Neutropenia in agammaglobulinemia Gram-negative septicemia)

Neutropenia in patients with congenital chromosomal Drug-induced neutropenia (chemotherapy-induced and abnormalities idiosyncratic)

Some rare metabolic disorders Neutropenia associated with (hypersplenia)

Neutropenia associated with bone marrow suppression Congenital dysgranulopoietic neutropenia (malignancies)

NEUTROPHILIA

Neutrophil counts are known to be physiologically elevated in pregnancy and in newborns, compared to other groups. When the neutrophil count is abnormally high compared to the demographic-specific reference range, it is called . It is one of the most frequently observed blood count changes.6,15,16

Shift neutrophilia, which is usually a transient condition, results from a shift of cells from the marginal to the circulating granulocyte pool without any quantitative change in the total blood granulocyte pool (TBGP). Strenuous exercise, electric , emotional states, vomiting, convulsions, paroxysmal tachycardia and epinephrine injection are the most frequent causes of shift neutrophilia.12

10 Learning Guide: WBC: Neutrophil Granulocytes True neutrophilia is either due to an increase in the rate of release of neutrophils from the bone marrow or an increase in the production of neutrophils (increased rate of granulocytopoiesis), resulting in a true increase in the TBGP. The most common cause of neutrophil is acute infection with a pyogenic . However, neutrophil leukocytosis also occurs in infections with certain non-pyogenic (e.g., in poliomyelitis, herpes zoster and typhus). Neutrophilia is a hallmark of but can also be a manifestation of a myeloproliferative neoplasm such as chronic myeloid leukemia (CML). CML is characterized by an increased neutrophil count (usually > 50 x 109/L), associated with a and prominent presence of myelocytes. and/or may also be present.

Causes of neutrophilia7,12 are listed in the Table 3 below.

TABLE 3. CAUSES OF NEUTROPHILIA

CAUSES OF PHYSIOLOGIC CAUSES OF PATHOLOGIC NEUTROPHILIA NEUTROPHILIA

Acute infections Neonates Acute (surgery, burn, necrosis, systemic autoimmune disorders, etc.)

Endocrine/metabolic disorders (Cushing syndrome, thyrotoxicosis, diabetes, uremia, gout, etc.) Exercise Acute hemorrhage and acute hemolysis

Myeloproliferative neoplasms Emotional Stress Malignant diseases: carcinoma, lymphoma, other solid tumors

Drugs: adrenaline, corticosteroids, lithium Pregnancy, Parturition, Lactation Asplenia and some rare inherited disorders

LEFT SHIFT

During increased production and accelerated release of neutrophils from the bone marrow, less mature forms can appear in the peripheral blood. The most frequently seen cell types are band neutrophils, but and even earlier forms can be present. This phenomenon is referred to as “left shift” and is usually associated with neutrophilia. Left shift can be defined as the increase in the ratio of non-segmented (band) to segmented neutrophils in the peripheral blood.15,17 Normally, band forms constitute up to 10% of the white cells in the blood of healthy adult individuals but can be present in higher concentrations physiologically during pregnancy and in newborns.12

Learning Guide: WBC: Neutrophil Granulocytes 11 The most common cause of a left shift is inflammation, because inflammatory stimulate both neutrophil production and release of mature and immature forms from the bone marrow. Toxic conditions or other severe illnesses, such as hypoxia, shock, major trauma or septicemia can also cause a left shift. In certain circumstances, infection may be associated with a failure to adequately increase effective granulocytopoiesis or with an exhaustion of the marrow granulocyte pool. In these cases, neutropenia may be seen together with a left shift. This is particularly common in very severe bacterial infections or in bacterial infections in neonates and alcoholics.

Although left shift is typically a sign of infection and inflammation, left-shifted may also be observed in certain myeloid malignancies. In addition, treatment with GM-CSF (as part of mobilization, or as treatment after bone marrow transplantation and in immunosuppressed patients) may cause iatrogenic left shift.

Morphologically, it can be challenging to differentiate band neutrophils from mature (segmented) neutrophils on peripheral blood smears.15 Counting band neutrophils has been shown to be subjective and is traditionally associated with high within- and between-reader variability and unsatisfactory reproducibility; therefore, it is suggested to have limited clinical value.18 Automated analyzers report band neutrophils as part of segmented neutrophils in WBC differenial results, in accordance with recommendations from ICSH;15 however, most of them can display an alert or flag in the presence of left- shifted granulopoiesis.

IMMATURE GRANULOCYTES

Promyelocytes, myelocytes and metamyelocytes are collectively defined as immature granulocytes. They are found in bone marrow, and are not normally present in the peripheral blood, except for newborns. During inflammation or infection, the maturation time for neutrophils may be reduced from approximately 10 to 2 days, and immature forms may be released to the circulation.7

Immature granulocytes (IG) traditionally have been identified and counted during microscopic WBC differentiation, using features such as cell size, shape, pattern and cytoplasmic appearance and pattern.

Some fully automated hematology analyzers can enumerate immature granulocytes and report them as an absolute IG count, and as percentage of WBC (% IG), along with the rest of the WBC differential. With modern hematology analyzers providing automated IG counts based on many thousands of WBC events, it is not rare to see healthy subjects with absolute and % immature granulocytes above zero. Table 4 below lists IG count reference ranges in healthy individuals reported by two studies.19,20

12 Learning Guide: WBC: Neutrophil Granulocytes TABLE 4. EXPECTED RANGES OF IMMATURE GRANULOCYTES IN HEALTHY INDIVIDUALS

ABSOLUTE IG COUNT AGE %IG (x 109/L)

≤10 Years ≤ 0.04 ≤ 0.3%

>10 years ≤ 0.07 ≤ 0.9%

Adults ≤ 0.03 ≤ 0.42%

CLINICAL IMPORTANCE OF IMMATURE GRANULOCYTES

The presence of immature granulocytes in the peripheral blood reflects increased production and can be a sign of reactive and neoplastic conditions. These include infections (especially of bacterial origin) or severe inflammatory diseases. The IG count and %IG are considered screening and prognostic tools for sepsis, bacteremia or severe infection. In one study, the IG concentration was monitored in ICU patients and it was found to have the highest discriminating power for diagnosing infection. Patients with an infection had significantly higher mean IG concentration than those without an infection (P < 0.0001). Based on these data, IG concentration may differentiate patients with or without infection during early phases of systemic inflammatory response.21

Immature granulocytes are also frequently seen in myeloproliferative diseases such as CML, acute promyelocytic leukemia and myelofibrosis, and in metastatic bone marrow infiltration by a malignancy. Accordingly, enumerating and classifying IG can be helpful for detecting and sometimes monitoring these diseases.22-23

Reliable automated blood cell characterization and quantification remain challenging in pathological samples, partly due to the potential presence of concomitant morphological abnormalities (e.g., hypogranulation or pseudo-Pelger-Huët).

IG concentrations must be interpreted in conjunction with clinical symptoms and other laboratory markers such as WBC and neutrophil granulocyte counts, acute phase protein concentrations and microbiology results.

Learning Guide: WBC: Neutrophil Granulocytes 13