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 antibiotic treatment or even surgery. It's crucial not to miss this diagnosis due to its potential for serious complications.
  • Septic Arthritis: An infection within a joint, which is a medical emergency requiring immediate attention to prevent permanent damage.
  • Cellulitis: A bacterial skin infection that can spread rapidly and requires prompt antibiotic treatment.
• Rare Diagnoses
  • Erythema Multiforme: An immune-mediated condition that can cause skin lesions, including on the hands, though it's less common to present solely as swelling and redness at the base of the thumb nail.
  • Psoriatic Nail Dystrophy: Part of psoriasis, which can cause changes in the nails and surrounding skin, including swelling and redness, though it's typically accompanied by other symptoms.
  • Glomus Tumor: A rare, benign tumor of the glomus body, which can cause pain and swelling under the nail, though it's more commonly associated with a specific type of pain and less with infection-like symptoms.