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970 Part VII: Neutrophils, Eosinophils, Basophils, and Mast Cells Chapter 63: Basophils, Mast Cells, and Related Disorders 971

BASOPHILOPENIA and significant drop in blood basophil levels of up to 50 percent has
108
Because numbers of blood basophils can be very low even in apparently been documented at ovulation. A few patients with an apparent total
32,34
normal individuals, 8–10,102 determining whether examples of basophilope- lack of basophils have been reported.
nia reflect pathologic processes as opposed to normal variation can be A morphologic abnormality expressed in the majority of eosino-
difficult. Nevertheless, reduced numbers of circulating basophils have phils and basophils but not in other leukocytes or mast cells has been
been reported in several disorders (Table 63–2). Basophilopenia has described as an autosomal dominant condition affecting four members
33
been recorded in association with urticaria and anaphylaxis, 105,106 but of a family. Cytoplasmic inclusions and crystals in basophils resem-
the extent to which the latter finding represents a loss of metachromatic bling the May-Hegglin anomaly have occurred in healthy individuals.
staining of circulating degranulated cells rather than a true decrease in
the number of cells is undetermined. Basophilopenia occurs in condi- BASOPHILIA
tions that also are associated with eosinophilopenia. These conditions
often are associated with increased secretion of adrenal glucocorti- Table 63–2 lists conditions associated with increased numbers of blood
coids. 102,107,108 Basophil counts may diminish, sometimes markedly, basophils (basophilia).
during leukocytosis accompanying infection, inflammatory states,
immunologic reactions, neoplasia, or hemorrhage. Basophil counts Inflammatory and Immunologic Responses
107
also are diminished in thyrotoxicosis or after pharmacologic admin- An increased number of basophils is commonly associated with
istration of thyroid hormones. Conversely, basophil counts may be chronic, IgE-associated hypersensitivity disorders. These disorders
increased in myxedema or after ablation of thyroid function. A rapid often are accompanied by increased levels of IgE. Although serum
107
IgE levels and basophil numbers are not directly related, increased
109
IgE levels are associated with increased expression of FcεRI on the
surfaces of both basophils and mast cells. 72,73,110 Moreover, basophils
TABLE 63–2. Conditions Associated with Alterations in can be recruited into tissues at sites of IgE-associated and other
Numbers of Blood Basophils immunologic responses. 1,4,5,55–57,77 Basophil levels may be elevated
in ulcerative colitis and juvenile rheumatoid arthritis, whereas
112
111
I. Decreased Numbers (Basopenia) many inflammatory conditions that cause a leukocytosis are associ-
A. Hereditary absence of basophils (very rare) ated with basophilopenia. Basophilia can occur in subjects exposed
B. Elevated levels of glucocorticoids to ionizing radiation. 113
C. Hyperthyroidism or treatment with thyroid hormones
D. Ovulation Clonal Myeloid Diseases
Myeloproliferative Neoplasms The concentration of blood
E. Hypersensitivity reactions basophils is slightly increased in many patients with polycythemia vera
1. Urticaria (Chap. 84), primary myelofibrosis (Chap. 86), and essential thrombo-
2. Anaphylaxis cythemia (Chap. 85). A slight increase in the absolute basophil count
3. Drug-induced reactions may be a useful early sign of a myeloproliferative neoplasm. An increased
F. Leukocytosis (in association with diverse disorders) absolute basophil count occurs in virtually all patients with chronic
II. Increased Numbers (Basophilia) myelogenous leukemia (CML). 114–116 In some patients, basophils can
A. Allergy or inflammation represent 20 to 90 percent of blood leukocytes (Chap. 89). Exaggerated
basophilia of this type is a poor prognostic sign and may herald transfor-
1. Ulcerative colitis mation to the accelerated phase of CML. The basophil in myeloprolif-
117
2. Drug, food, inhalant hypersensitivity erative neoplasms is derived from the malignant clone and in CML can
118
3. Erythroderma, urticaria contain the Philadelphia (Ph) chromosome. The basophils in CML
4. Juvenile rheumatoid arthritis exhibit a variety of ultrastructural and biochemical abnormalities. 119,120
B. Endocrinopathy In some cases, the abnormalities obscure the typical distinctions
between basophils and mast cells.
Release of basophil-associated
121–124
1. Diabetes mellitus histamine can lead to episodes of flushing, pruritus, and hypotension in
2. Estrogen administration occasional patients with basophilic CML. 125,126 Severe peptic ulcer of the
3. Hypothyroidism (myxedema) stomach and duodenum can occur in association with hypersecretion of
C. Infection gastric acid and pepsin. 127,128 Ph chromosome–positive acute basophilic
1. Chicken pox leukemia may be a presenting manifestation of CML. 129
Basophilic Leukemias The basis for designating some cases as
2. Influenza basophilic leukemias as opposed to examples of other more typical
3. Smallpox myelogenous leukemias with an associated pronounced basophilia is
4. Tuberculosis not always clear. Accordingly, we refer to these conditions herein as
D. Iron deficiency leukemias associated with basophilia. Table 63–3 lists the leukemias
E. Exposure to ionizing radiation associated with basophilia. In addition to extreme basophilia in the
F. Neoplasia chronic phase CML or as a manifestation of the accelerated phase
of CML, acute basophilic leukemia can rarely occur de novo.
130–136
1. “Basophilic leukemia” (see text) Thus, acute basophilic leukemia is included in the World Health Orga-
G. Myeloproliferative neoplasms (especially chronic myeloge- nization classification of acute myeloid leukemias (AMLs), but the
137
nous leukemia; also polycythemia vera, primary myelofibro- entity is poorly defined. 135,136,138 Some cases are recognized only by
sis, essential thrombocythemia) electron microscopy, a procedure not used routinely in the diagnosis
H. Carcinoma or classification of leukemias. One report suggests that the detection

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