Differential Diagnosis

The question seems to be referring to a condition that starts in the finger and has no relation to the genitals. Based on this information, here's a differential diagnosis:

• Single most likely diagnosis:
  • Herpes Simplex Virus (HSV) infection limited to the finger (Herpetic Whitlow): This is a plausible diagnosis because HSV can cause lesions on the fingers, known as herpetic whitlow, without any genital involvement.
• Other Likely diagnoses:
  • Eczema or Dermatitis: Conditions like eczema or dermatitis can start in the fingers and are not related to genital health.
  • Paronychia: An infection around the nail, which can occur without any relation to the genitals.
  • Warts: Caused by the Human Papillomavirus (HPV), warts can appear on the fingers and are unrelated to genital warts.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.):
  • Sporotrichosis: A fungal infection that can start in the finger after a skin prick injury, especially in gardeners. It's crucial to diagnose early to prevent spread.
  • Melanoma: Although rare, a new or changing lesion on the finger could potentially be a sign of melanoma, which is deadly if not caught early.
• Rare diagnoses:
  • Sarcoidosis: A condition that can cause skin lesions, including on the fingers, but it's rare and usually associated with systemic symptoms.
  • Leprosy (Hansen's Disease): Can cause skin lesions and nerve damage, starting in the fingers, but it's very rare in most parts of the world.

Each of these diagnoses has a brief justification based on the information provided, focusing on conditions that could start in the finger without any relation to the genitals. The categorization aims to prioritize both likelihood and potential impact on health.