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CHAPTER 47 ■ LYMPHADENOPATHY
KIYETTA H. ALADE, BETH M. D’AMICO

INTRODUCTION
Lymphadenopathy, defined as an enlargement of lymph nodes, is a frequent presenting
sign in children. Most illnesses causing lymphadenopathy are common viral or bacterial
infections that improve spontaneously or with an appropriate course of antimicrobial
therapy. However, some serious illnesses, including malignancies, can present first as
lymphadenopathy. Thus, a focused history, thorough physical examination, and
knowledge of various causes of adenopathy are important in formulating an appropriate
differential diagnosis.

MECHANISM OF LYMPHADENOPATHY
Enlargement of lymph nodes can be due to physiologic or pathologic causes. Most
commonly, when lymph nodes perform their normal function, antigenic stimulation
causes proliferation of lymphocytes, and nodes increase in size. This response is
particularly active in children, who are frequently exposed to new antigens, thus
accounting for the common observation of lymphadenopathy associated with pediatric
infections. A second cause of lymph node enlargement occurs when bacteria or other
pathogens that are present in lymphatic fluid stimulate an influx of inflammatory cells,
local cytokine release, and symptoms of lymphadenitis. These include enlargement of the
node, erythema, edema, and tenderness of the overlying skin. A third cause of adenopathy
is neoplastic disease, where malignant cells originate in or migrate to lymph nodes,
infiltrating the node and causing enlargement. Lastly, in rare cases, genetic storage
diseases may lead to deposition of foreign material within the node.
A number of studies have described the presence of palpable lymph nodes in healthy
infants and children. A seminal study of well infants and children up to 6 years of age
reported more than half of the children had palpable nodes, most commonly in the
cervical, occipital, and submandibular regions. It is commonly accepted that lymph nodes
in the cervical and axillary regions up to 1 cm in diameter, nodes in the inguinal region up
to 1.5 cm in diameter, and nodes in the epitrochlear region up to 0.5 cm in diameter are

considered normal in children.

DIFFERENTIAL DIAGNOSIS
As the differential diagnosis of lymphadenopathy is extensive, it is helpful to distinguish
localized from generalized lymphadenopathy, and an acute from chronic time course.
Localized adenopathy includes lymphadenopathy in a single region, and generally occurs
in response to a focal infectious process. Generalized lymphadenopathy is defined as
enlargement of more than two noncontiguous lymph node regions. The most common
causes of generalized adenopathy are systemic infections, autoimmune diseases, and