What are the common infectious causes of lymphadenopathy that I should consider in a primary care setting?

Common infectious causes of lymphadenopathy in primary care include viral, bacterial, and less commonly mycobacterial infections.

• Viral infections are frequent causes, especially upper respiratory tract viruses such as Epstein-Barr virus (EBV), cytomegalovirus (CMV), and human immunodeficiency virus (HIV). These viruses often cause generalized or localized lymphadenopathy and should be considered particularly if there are systemic symptoms or risk factors present. Appropriate investigations and management should be arranged based on clinical judgement NICE CKS.
• Bacterial infections commonly causing lymphadenopathy include those related to skin and soft tissue infections (e.g., boils, carbuncles, staphylococcal carriage), dental infections (gingivitis, periodontitis), and ear infections (otitis externa, otitis media), as well as sinusitis and acute sore throat. Antibiotic treatment may be considered depending on the likely source, but antibiotics should not be routinely prescribed unless there are clear signs of bacterial infection to avoid masking serious conditions NICE CKS.
• Mycobacterial infections, such as tuberculosis, should be considered especially in persistent or supraclavicular lymphadenopathy, and chest X-ray may be warranted to exclude tuberculosis or sarcoidosis NICE CKS.
• Other atypical infections may be considered if lymphadenopathy persists beyond 2–4 weeks or does not respond to initial treatment, warranting further specialist referral and targeted blood tests NICE CKS.
• From the literature perspective, infectious causes remain the most common etiology of lymphadenopathy in primary care, with viral infections predominating. Bacterial infections are often localized and related to adjacent sites of infection. Less common infectious causes include atypical mycobacteria and other granulomatous infections, which may require more extensive evaluation Ferrer 1998Rodolfi et al. 2024.

In summary, primary care clinicians should consider common viral infections (EBV, CMV, HIV), bacterial infections related to local sites (skin, dental, ear, throat), and mycobacterial infections when evaluating lymphadenopathy. Persistent or unexplained cases warrant further investigation and possible referral NICE CKS Ferrer 1998Rodolfi et al. 2024.