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1200 Part IX: Lymphocytes and Plasma Cells Chapter 79: Lymphocytosis and Lymphocytopenia 1201

TABLE 79–1. Causes of Lymphocytosis
I. Primary lymphocytosis B. Bordetella pertussis 62
A. Lymphocytic malignancies C. NK cell lymphocytosis 72
1. Acute lymphocytic leukemia (Chap. 91) D. Stress lymphocytosis (acute) 91
2. Chronic lymphocytic leukemia and related disorders 1. Cardiovascular collapse 171
(Chap. 92) a. Acute cardiac failure
3. Prolymphocytic leukemia (Chap. 92) b. Myocardial infarction
4. Hairy cell leukemia (Chap. 93) 2. Staphylococcal toxic shock syndrome 172
5. Adult T-cell leukemia (Chaps. 92 and 104) 3. Drug-induced 89
6. Leukemic phase of B-cell lymphomas (Chap. 95) 4. Major surgery
7. Large granular lymphocytic leukemia (Chap. 94) 5. Sickle cell crisis 173
a. Natural killer (NK) cell leukemia (Chap. 104) 6. Status epilepticus
b. CD8+ T-cell large granular lymphocytic leukemia 7. Trauma
c. CD4+ T-cell large granular lymphocytic leukemia E. Hypersensitivity reactions
d. γ/δ T-cell large granular lymphocytic leukemia 1. Insect bite 101
B. Monoclonal B-cell lymphocytosis (Chap. 92) 2. Drugs 102–104
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C. Persistent polyclonal B cell lymphocytosis 26,29 F. Persistent lymphocytosis (subacute or chronic)
II. Reactive lymphocytosis 1. Cancer 112
A. Mononucleosis syndromes (Chap. 82) 2. Cigarette smoking 51
1. Epstein-Barr virus 55 3. Hyposplenism 116
2. Cytomegalovirus 58 4. Chronic infection
3. HIV (Chap. 81) a. Leishmaniasis 174
164
4. Herpes simplex virus type II b. Leprosy
5. Rubella virus 165 c. Strongyloidiasis 75
6. Toxoplasma gondii 117 5. Thymoma 109,111
7. Adenovirus
8. Infectious hepatitis virus 166
9. Dengue fever virus 167,168
10. Human herpes virus type 6 (HHV-6) 169
11. Human herpes virus type 8 (HHV-8) 170
12. Varicella zoster virus 165

Clinical MBL is more commonly encountered in clinical practice recommended in screening MBL. Clinical MBL should also be coun-
when patients are evaluated for lymphocytosis. A prospective study seled about screening for second primary malignancies. Table 79–2 lists
evaluated classic and new prognostic markers (IGHV mutational status the features of screening MBL and clinical MBL.
and chromosomal abnormalities) in patients with clinical MBL and Rai
stage 0 CLL. No significant differences were found either in IGHV/ Persistent Polyclonal Lymphocytosis of B Lymphocytes
16
IGHD/IGHJ usage between the two patient groups. Similar gene and Persistent polyclonal B-cell lymphocytosis (PPBL) is defined as a chronic,
microRNA (miRNA) signatures were seen in both groups suggesting moderate increase in absolute lymphocyte counts (>4 × 10 /L) without
9
that the two conditions have an indistinguishable biologic profile but evidence for infection or other conditions that can increase the lympho-
differ only in the initial size of the monoclonal population. This con- cyte count. This type of lymphocytosis is a rare disorder that mostly
17
25
dition is biologically indistinguishable from CLL. Given the seriousness affects middle-age women and is associated with smoking. It is char-
of a diagnosis of CLL, investigators have sought to evaluate how the acterized by the persistent expansion of CD27+immunoglobulin (Ig)
B-cell clone relates to the clinical outcome of development into CLL. 16,18 M+IgD+ B cells, the presence of circulating binucleated lymphocytes
The consensus is that the risk of progression requiring CLL-specific and increased IgM serum levels. 26,27 Such patients have an accumulation
treatment among individuals with clinical MBL is 1 to 2 percent per of polyclonal B cells that have an unusual binucleated appearance on the
year compared to 5 to 7 percent per year for individuals with Rai stage blood film. Specific morphologic features predictive of the diagnosis
28
0 CLL. 6,10,19–22 In contrast to this quantifiable progression for clinical include basophilic vacuolated cytoplasm and monocytoid changes. 28,29
MBL, progression to CLL is extremely rare among individuals with These lymphocytes typically have low-to-negligible expression of CD5
screening MBL. In addition, a cohort study showed that clinical or CD23 found in patients with CLL and are polyclonal with respect
23
MBL was an independent risk factor for hospitalization for infection to light-chain expression and immunoglobulin heavy-chain gene rear-
after controlling for age and gender compared to a control cohort. rangements (Fig. 79–1). 30,31
24
Thus, individuals with clinical MBL should be followed with a physi- The B cells commonly express relatively high levels of IgD and
cal examination and complete blood counts by a hematologist every 6 CD27, a phenotype shared with that of memory B cells (Chap. 75).
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to 12 months, while longer followup intervals of 12 to 18 months are Consistent with this phenotype, the immunoglobulin variable-region

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