Lymphadenitis

Lymphadenitis is inflammation of one or more lymph nodes, usually due to infection or, less commonly, noninfectious inflammatory or malignant processes. It typically presents as tender, enlarged lymph nodes and may be accompanied by fever, malaise, or localized signs related to the primary infection. Lymphadenitis can be localized to a region near a primary source of infection or, less commonly, involve nodes throughout the body (generalized lymphadenitis).

Most cases of acute lymphadenitis are bacterial, commonly due to Staphylococcus aureus or Streptococcus species, arising from nearby skin, dental, or upper respiratory infections. Other causes include viral infections causing reactive nodes, mycobacterial or fungal infections, and cat scratch disease. Noninfectious causes include autoimmune diseases and malignancies such as lymphoma or leukemia. The infection or inflammation typically leads to lymph node enlargement with possible warmth and erythema of the overlying skin; fluctuant nodes may indicate an abscess.

Diagnosis relies on clinical evaluation supported by laboratory tests and imaging. Blood tests such as complete blood count and inflammatory markers (CRP, ESR) can indicate infection. Ultrasound is useful to assess node size, structure, and the presence of an abscess; biopsy or fine-needle aspiration may be required if nodes are hard, fixed, supraclavicular, or if cancer or tuberculosis is suspected. Cultures or PCR from aspirates can identify pathogens; TB testing and HIV testing may be appropriate in select cases.

Treatment targets the underlying cause. Localized bacterial lymphadenitis is usually treated with appropriate antibiotics; abscesses may require drainage. Severe, systemic, or nonresponding cases may require hospitalization and intravenous antibiotics. Noninfectious etiologies are managed according to the specific diagnosis (e.g., treating autoimmune disease or malignancy). Prognosis is generally favorable with prompt treatment, though complications such as abscess formation, sepsis, or persistent nodal enlargement can occur.