Diagnostic Approach and Management of Thumb Swelling in Children

Initial Assessment and Diagnosis

The presence of fever suggests either bacterial infection requiring antibiotics or hand-foot-and-mouth disease (HFMD) as part of the viral prodrome, according to the American Academy of Pediatrics 1
Vesicular lesions on the thumb strongly suggest HFMD, which commonly presents with fever and vesicles on hands, feet, and mouth, as noted by the Centers for Disease Control and Prevention 1
Oral examination is crucial to check for mouth sores, ulcers, or vesicles on the tongue, buccal mucosa, or palate, which would confirm HFMD, as recommended by the World Health Organization 1
Localized warmth with tenderness suggests bacterial cellulitis; fluctuance indicates abscess formation requiring drainage, according to the Infectious Diseases Society of America 2, 3
Swelling and redness around the nail suggests paronychia, which may be bacterial or herpetic, as stated by the American Academy of Dermatology 2

For HFMD, supportive care includes pain management with acetaminophen (15 mg/kg every 4-6 hours) or ibuprofen (10 mg/kg every 6-8 hours) for fever and discomfort, as suggested by the American Academy of Pediatrics 1
Topical zinc oxide can be applied to thumb lesions after gentle cleansing to reduce itchiness and provide barrier protection, as recommended by the National Institute of Health 1
For bacterial infections, first-line antibiotic treatment is amoxicillin-clavulanate 45 mg/kg/day divided twice daily for 5-7 days to cover Staphylococcus aureus, Streptococcus pyogenes, and anaerobes, as recommended by the American Academy of Pediatrics 3
For herpetic whitlow, oral acyclovir (20 mg/kg, maximum 400 mg) five times daily for 7-10 days is recommended if started within 72 hours of symptom onset, as stated by the Centers for Disease Control and Prevention 1

Reassess at 48-72 hours if bacterial infection is suspected and antibiotics are initiated, expecting improvement in redness, warmth, and swelling, as recommended by the Infectious Diseases Society of America 3
Monitor for late sequelae of HFMD, including Beau's lines (nail grooves) and periungual desquamation, which are benign and self-resolving, as noted by the World Health Organization 1