Differential Diagnosis for Swelling and Redness at Base of Thumb Nail

• Single Most Likely Diagnosis
  • Paronychia: This is an infection of the skin around the nail, which is a common condition that can cause swelling and redness at the base of the thumb nail. It is often caused by bacterial infection, and the location and symptoms described make it the most likely diagnosis.
• Other Likely Diagnoses
  • Herpetic Whitlow: A viral infection caused by herpes simplex virus, leading to painful swelling and redness, typically at the fingertip but can occur near the nail.
  • Nail Bite or Pick Infection: Infections resulting from biting or picking at the nails, which can introduce bacteria into the skin around the nail.
  • Ingrown Nail: Although more common in the toes, an ingrown nail can occur in the fingers and cause redness and swelling, especially if it becomes infected.
• Do Not Miss Diagnoses
  • Osteomyelitis: An infection of the bone, which, although rare, can occur in the fingers and would require prompt treatment to prevent serious complications.
  • Septic Arthritis: An infection within a joint, which is a medical emergency requiring immediate attention to prevent joint destruction.
  • Cellulitis: A bacterial skin infection that can spread rapidly and requires antibiotic treatment.
• Rare Diagnoses
  • Erythema Multiforme: An immune-mediated condition that can cause skin lesions, including around the nails, but is less common and typically associated with other systemic symptoms.
  • Psoriatic Nail Dystrophy: Part of psoriasis, which can cause changes in the nails and surrounding skin, including swelling and redness, but usually presents with other characteristic skin lesions.
  • Squamous Cell Carcinoma: A type of skin cancer that can very rarely present as swelling and redness around the nail, especially in individuals with significant sun exposure or other risk factors.