Lymphadenitis, a localized infection of lymph glands, is a common reason for hospital admission in pediatric patients. The cells in lymph glands typically proliferate in the setting of infection; a focal lymph node infection can proceed to organization of a focal abscess in the soft tissue and cellulitis of the overlying skin.¹ Because lymphatic drainage is regional, the involved nodes often reflect a distal primary infection or a systemic illness affecting multiple groups of lymph nodes. It is important to distinguish lymphadenitis from nonlymphatic processes and from lymphadenopathy—swollen, reactive nodes—secondary to other diseases.

A detailed history can be invaluable in determining the likely causes of localized lymph node swelling in a pediatric patient (Table 31-1). The history can help determine systemic involvement, the risk of serious underlying diagnoses, and possible infectious exposures. It is useful to define the chronology of the illness and the location and progression of the process. The pertinent health history includes any major illnesses, dysmorphologies or diagnosed syndromes, previous dental and surgical procedures, prior swellings, and recent infections.

The physical examination includes evaluation of the region of the lymphadenitis as well as a general examination of other lymph nodes and organ systems (Table 31-2). Note should be taken of whether the swelling is unilateral or bilateral, and whether it involves a single lymph node chain or multiple chains. The extent of local erythema, induration, or fluctuance along with possible tracks or defined margins should be delineated, and sites that drain to the involved nodes should be examined for signs of infection^1,2 (Table 31-3). To follow the progression of the process during subsequent evaluations, it can be useful to outline the borders of the indurated or erythematous area with a nontoxic marking pen.

In determining possible causes of suspected lymphadenitis, the location of the lesion plays an important role, as do other components of the history and physical examination. Lymphadenitis can affect any regional lymph nodes; head and neck, axillary, and inguinal nodes are the most common sites of infection in children. The differential diagnosis for involved lesions includes bacterial, mycobacterial, fungal, and viral processes, as well as noninfectious causes (Table 31-4).