Differential Diagnosis for Semisolid Papule on Dorsal Finger with Clear Drainage and Pain

• Single Most Likely Diagnosis
  • Herpes Simplex Virus (HSV) infection: This is a common cause of painful, semisolid papules with clear drainage, especially if the patient has a history of similar outbreaks. The location on the dorsal finger is less typical than the more common perioral or genital areas, but it's still within the realm of possibility, especially if the infection was acquired through direct contact.
• Other Likely Diagnoses
  • Paronychia: An infection of the skin around the nail, which can present with a painful, semisolid papule and clear drainage. It's a common condition, especially in individuals who frequently immerse their hands in water or have nail biting habits.
  • Folliculitis: An inflammation of the hair follicles, which can cause papules or pustules that may drain. While it's more common in areas with denser hair follicles, it could occur on the dorsal finger, especially if there's an ingrown hair or irritation.
  • Abscess: A localized collection of pus that can form a painful, semisolid mass with drainage. It could occur on the finger due to a bacterial infection, often Staphylococcus aureus.
• Do Not Miss Diagnoses
  • Erysipelas: A type of skin infection that involves the upper dermis, typically caused by beta-hemolytic group A Streptococcus. It can present with a painful, well-demarcated, semisolid lesion and is important to diagnose early due to the risk of complications like sepsis or abscess formation.
  • Cellulitis: A bacterial infection of the skin and subcutaneous tissues, which can cause redness, swelling, warmth, and pain. While it typically doesn't form a semisolid papule, it's crucial to consider due to the potential for serious complications if not treated promptly.
• Rare Diagnoses
  • Keratoacanthoma: A low-grade, or sometimes considered benign, malignancy that can present as a firm, semisolid papule. It's less likely given the description of clear drainage and pain but should be considered in the differential for any new, unexplained skin growth.
  • Mycobacterial Infection: Certain mycobacteria, like Mycobacterium marinum, can cause skin infections (such as "fish tank granuloma") that might present with papules or nodules, especially after exposure to contaminated water. These infections are rare but could be considered in individuals with a relevant history of exposure.