Differential Diagnosis for Blood Under Nail Bed

• Single Most Likely Diagnosis
  • Subungual hematoma: This is the most common cause of blood under the nail bed, usually resulting from trauma to the nail, such as hitting the finger with a hammer or dropping something on it. The blood accumulates between the nail plate and the nail bed, causing pain and discoloration.
• Other Likely Diagnoses
  • Nail psoriasis: This condition can cause bleeding under the nail due to inflammation and lifting of the nail plate from the nail bed.
  • Onychomycosis (fungal infection of the nail): Although less common, fungal infections can lead to nail lifting and subsequent bleeding under the nail.
  • Trauma (non-accidental): Intentional injury can also cause subungual hematoma.
• Do Not Miss Diagnoses
  • Subungual melanoma: A type of skin cancer that can present with bleeding under the nail. It is crucial to distinguish this from a benign hematoma because of its potential for metastasis and high mortality if not treated early.
  • Subungual glomus tumor: A rare, benign tumor that can cause pain, bleeding, and discoloration under the nail. Although not typically life-threatening, it can significantly affect quality of life if not diagnosed and treated.
• Rare Diagnoses
  • Scurvy: Vitamin C deficiency can lead to poor wound healing and bleeding under the nails, among other symptoms.
  • Vasculitis: Certain types of vasculitis can affect the small blood vessels under the nail, leading to bleeding.
  • Systemic diseases (e.g., lupus, rheumatoid arthritis): These conditions can have manifestations that include nail changes and bleeding, though they are less common presentations.