Epidemiology & Risk Factors

Most common cause of acute unilateral suppurative lymphadenitis in children < 5 yo.
Pathogens:
- Staphylococcus aureus (> 50% of cases). c
- Group A Streptococcus (S. pyogenes).
- Anaerobes (Peptostreptococcus, Bacteroides): associated with poor dental hygiene/periodontal disease.
Risk factors:
- Recent URI or pharyngitis.
- Dental caries or oral mucosal trauma.
- Impetigo or facial skin infections.

Clinical Features

Rapid onset (1-5 days) of localized symptoms.
Unilateral enlargement of a single submandibular or anterior cervical node.
Physical Exam:
- Swollen, warm, erythematous, and exquisitely tender lymph node.
- Fluctuance indicates suppuration/abscess formation.
Systemic findings:
- High fever, irritability, lethargy, poor oral intake.
- Torticollis or limited neck ROM (if deep space extension).

Initial/Screening: Clinical diagnosis in mild, early presentations without signs of fluctuance.
Imaging:
- Ultrasound (US) of the neck: Test of choice to detect fluctuance/abscess formation vs cellulitis/phlegmon.
- CT neck with IV contrast: Reserved for suspicion of deep neck space infection (e.g., retropharyngeal abscess).
Key Labs:
- CBC: Leukocytosis with left shift.
- Inflammatory markers: ↑ CRP, ↑ ESR.
Microbiology:
- Gram stain & culture of purulent fluid (aspirated via needle or during I&D).
- Blood cultures if toxic appearance, high fever, or immunocompromised.

Non-tuberculous Mycobacteria (NTM):
- Diff: Subacute/chronic course (> 3-4 weeks), painless/nontender, characteristic violaceous skin discoloration, non-fluctuant initially, unresponsive to standard empiric Abx.
Bartonella henselae (Cat-scratch disease):
- Diff: Subacute indolent course, history of cat scratch/flea contact, primary papule at scratch site, nodes commonly axillary/epitrochlear > cervical.
Acute Bilateral Viral Lymphadenitis (Adenovirus, EBV, Enterovirus):
- Diff: Bilateral, multiple small nodes, predominant systemic viral symptoms (rhinorrhea, cough, conjunctivitis). c
  - Bacteria: Direct focal entry & localized lymphatic drainage → unilateral
  - Virus: Hematogenous spread or widespread mucosal infection → bilateral
Kawasaki Disease:
- Diff: Unilateral cervical node (≥ 1.5 cm) associated with fever ≥ 5 days PLUS ≥ 4 features (conjunctivitis, mucosal changes, rash, extremity changes); non-purulent, unresponsive to Abx.
Branchial Cleft / Thyroglossal Duct Cyst:
- Diff: Superinfected congenital cyst; midline location (thyroglossal) or anterior border of SCM (branchial cleft), history of recurrent swelling.

Empiric Antimicrobial Therapy (Targeting S. aureus & S. pyogenes):
- Mild/Outpatient (Oral):
  - Clindamycin OR Amoxicillin-clavulanate (if low MRSA prevalence).
  - Cephalexin + TMP-SMX or Clindamycin alone (if MRSA suspected).
- Severe/Inpatient (IV) (for toxic appearance, infant < 3 mo, or failed outpatient oral Abx):
  - IV Clindamycin OR IV Ampicillin-sulbactam.
  - IV Vancomycin (if severe sepsis or high MRSA suspicion).
Surgical Intervention:
- Incision & Drainage (I&D) or Needle Aspiration:
  - Indicated if fluctuant mass or abscess confirmed on US.
  - Refractory to IV Abx therapy after 48-72 hours.

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