C h a p t e r 1 1
Disorders of White Blood Cells and Lymphoid Tissues
249
normal size, and rupture of the spleen is an infrequent
complication. In less than 1% of cases, mostly in the
adult age group, complications of the central nervous
system (CNS) develop. These complications include cra-
nial nerve palsies, encephalitis, meningitis, transverse
myelitis, and Guillain-Barré syndrome.
The peripheral blood usually shows an increase in
the number of leukocytes, with a white blood cell count
between 12,000 and 18,000 cells/
μ
L, 60% of which are
lymphocytes.
14
The rise in white blood cells begins dur-
ing the first week, continues during the second week of
the infection, and then returns to normal around the
fourth week. Although leukocytosis is common, leu-
kopenia may be seen in some persons during the first
3 days of illness. Atypical lymphocytes are common,
constituting more than 20% of the total lymphocyte
count. Heterophil antibodies usually appear during the
second or third week and decline after the acute illness
has subsided. They may, however, be detectable for up
to 9 months after onset of the disease.
Most persons with infectious mononucleosis recover
without incident. The acute phase of the illness usually
lasts for 2 to 3 weeks, after which recovery occurs rap-
idly. Some degree of debility and lethargy may persist
for 2 to 3 months. Treatment is primarily symptomatic
and supportive. It includes bed rest and analgesics such
as acetaminophen and nonsteroidal anti-inflammatory
drugs (NSAIDs) to relieve the fever, headache, and sore
throat. Although splenic rupture is rare, avoidance of
contact sports for a minimum of 3 weeks after diagnosis
is recommended.
15
In persons with immunodeficiency disorders that lead
to defects in cellular immunity (e.g., human immuno-
deficiency virus [HIV] infection, immunosuppressant-
treated recipients of organ or bone marrow transplants),
EBV infection may contribute to the development of
lymphoproliferative disorders (e.g., non-Hodgkin lym-
phoma).
12
These persons have impaired T-cell immunity
and are unable to control the proliferation of EBV-
infected B cells.
Neoplastic Disorders of
Hematopoietic and Lymphoid
Origin
The neoplastic disorders of hematopoietic and lymphoid
origin represent the most important of the white blood
cell disorders. They can be divided into two broad cat-
egories based on the origin of the tumor cells: lymphoid
neoplasms and myeloid neoplasms. The clinical features
of these neoplasms are largely determined by their site of
origin, the progenitor cell from which they originated,
and the molecular events involved in their transforma-
tion into a malignant neoplasm.
Myeloid neoplasms arise from hematopoietic stem
cells and normally give rise to monoclonal proliferations
that replace normal bone marrow cells. They include the
acute and chronic myelogenous leukemias.
4,7
The lym-
phoid neoplasms encompass a group of entities that vary
widely in their clinical presentation and behaviors. They
include the B- and T-cell leukemias and lymphomas (non-
Hodgkin and Hodgkin lymphomas) that originate in
peripheral lymphoid structures such as the lymph nodes,
where B and T lymphocytes undergo differentiation and
proliferation. The plasma cell dyscrasias originate in the
lymph nodes, where B cells differentiate into plasma cells.
Leukemias
The leukemias are malignant neoplasms of cells origi-
nally derived from precursor myeloid or lymphoid tis-
sue cells. The term
leukemia
(i.e., “white blood”) was
first used by Rudolf Virchow to describe a reversal of
the usual ratio of red blood cells to white blood cells.
16
syndrome, which is associated with severe
bacterial infections.The acquired neutropenias
encompass a wide spectrum of etiologies,
including immunologically mediated bone
marrow suppression, neutrophil injury and
destruction, infection-related processes, and
drug-induced mechanisms—particularly those
related to cancer chemotherapeutic agents.
■■
Infectious mononucleosis is a self-limited
lymphoproliferative disorder caused by the
B-lymphotropic Epstein-Barr virus that is
usually transmitted in the saliva.The disease is
characterized by fever, sore throat, generalized
lymphadenopathy, and the appearance of
atypical lymphocytes and several antibodies in
the blood, including the well-known heterophil
antibodies commonly used in its diagnosis.
Treatment is largely symptomatic and supportive
and most people recover without incident.
SUMMARY CONCEPTS
■■
Neutropenia, which represents a marked
reduction in neutrophils, can occur as a
congenital or acquired disorder. Because the
neutrophil is essential to host defenses against
bacterial and fungal infections, severe and often
life-threatening infections are common in persons
with neutropenia.
■■
Congenital neutropenia consists primarily of
cyclic neutropenia, which is characterized by
cyclic oscillations of peripheral neutrophils, and
severe congenital neutropenia or Kostmann
