Differential Diagnosis for a Vertical Hyperpigmentation Line Passing Through the Nail Bed

• Single Most Likely Diagnosis
  • Melanonychia: This condition is characterized by a vertical pigmented band in the nail plate, often due to the activation or proliferation of melanocytes in the nail matrix. It's the most common cause of a vertical hyperpigmentation line passing through the nail bed.
• Other Likely Diagnoses
  • Nail trauma: Trauma to the nail can cause inflammation and subsequent pigmentation, leading to a vertical hyperpigmentation line.
  • Nail infection (onychomycosis or paronychia): Certain infections can cause changes in nail pigmentation, including the appearance of a vertical line.
  • Systemic diseases (e.g., Addison's disease): Some systemic conditions can lead to nail changes, including hyperpigmentation.
• Do Not Miss Diagnoses
  • Subungual melanoma: Although rare, this is a potentially deadly condition that can present with a vertical hyperpigmentation line through the nail bed. Early detection is crucial for treatment and survival.
  • Subungual hematoma: Bleeding under the nail can cause a pigmented line and may be associated with trauma or other underlying conditions.
• Rare Diagnoses
  • Laugier-Hunziker syndrome: A rare condition characterized by hyperpigmentation of the nails, lips, and oral mucosa.
  • Peutz-Jeghers syndrome: An autosomal dominant disorder that can cause intestinal polyps and mucocutaneous melanin deposits, including in the nails.