📌 Mechanisms
• Physiologic hyperplasia (antigenic stimulation)
• Bacterial lymphadenitis (suppuration/abscess)
• Malignant infiltration (lymphoma, leukemia)
• Medication-induced (serum sickness)
• Storage diseases (Niemann-Pick, Gaucher)
🗺️ Regional Drainage
• Cervical: oropharynx, otitis, dental infections
• Supraclavicular: red flag (malignancy, TB, sarcoidosis)
• Axillary: arm/breast/chest wall
• Inguinal: lower extremity, STIs, UTI
⚠️ Red Flags
• Supraclavicular nodes → urgent imaging
• Size >2.5 cm, matted, fixed, rubbery
• Systemic symptoms: weight loss, night sweats, fever
• Generalized adenopathy + organomegaly
🦠 Common Causes
• Viral: EBV, CMV, HIV, adenovirus
• Bacterial: Group A strep, S. aureus, cat-scratch (Bartonella)
• Mycobacterial (TB, atypical)
• Toxoplasmosis, Kawasaki, PFAPA
💡 Diagnostic algorithm: Well-appearing + localized + infectious source → observation/antibiotics. Supraclavicular, progressive, or generalized → CBC, imaging, biopsy. Excision preferred for atypical mycobacteria to avoid sinus tracts.