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Lymphadenopathy, or enlarged lymph nodes, may be the result of acute or chronic inflammation, or infiltration via malignant cells. A lymph node measuring greater than 10 mm in longest diameter is generally considered enlarged. There are several exceptions to this rule: (1) epitrochlear nodes measuring more than 5 mm are abnormal; (2) inguinal nodes measuring more than 10–15 mm are abnormal; and (3) palpable supraclavicular, iliac, or popliteal nodes are always considered abnormal. Palpable lymph nodes are common in otherwise healthy infants and children as a result of reactive hyperplasia.1

Lymphadenitis is the term used to describe enlargement of lymph nodes due to inflammation. Cervical lymphadenitis refers to enlargement and inflammation of neck lymph nodes. Although there are no universally accepted definitions, in general, acute lymphadenitis is defined as inflammation developing over a few days, and subacute/chronic lymphadenitis occurs over weeks to months.2

Lymphadenitis is a common condition, although precise epidemiologic estimates are not available; in one study of school-age children, nearly one-third had palpable submandibular or cervical lymph nodes during a single examination.1

The duration of symptoms and laterality are key distinguishing features in the various causes of lymphadenitis (Table 29-1). Table 29-2 summarizes common infectious causes of lymphadenitis by presentation.

TABLE 29-1Key Characteristics in Differing Etiologies of Lymphadenitis
TABLE 29-2Differential Diagnosis for Infectious Causes of Cervical Lymphadenitis by Duration and Location

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