Differential Diagnosis for Violaceous Hyperpigmented Oval Patch

• Single most likely diagnosis
  • Mongolian spot: A benign congenital melanocytic lesion commonly found in infants, characterized by a violaceous hyperpigmented oval patch, typically on the lower back or buttocks. It usually fades by the age of two.
• Other Likely diagnoses
  • Ecchymosis: A bruise that can appear as a violaceous patch due to blood leakage into the skin, often resulting from trauma.
  • Hematoma: Similar to ecchymosis but involves a larger collection of blood outside of blood vessels, which can cause a violaceous discoloration.
  • Melasma: Although typically more brown than violaceous, melasma can sometimes appear with a bluish tint, especially in darker skin types, and is characterized by hyperpigmented patches usually on the face.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Malignant melanoma: Although less common, a new or changing violaceous patch could be a sign of melanoma, especially if it exhibits asymmetry, irregular borders, color variation, diameter over 6mm, or evolving size, shape, or color.
  • Kaposi's sarcoma: A type of cancer that can cause violaceous lesions on the skin, more common in immunocompromised individuals.
• Rare diagnoses
  • Phakomatosis pigmentovascularis: A rare condition characterized by the combination of vascular and pigmentary anomalies, which can include violaceous hyperpigmentation.
  • Erythema dyschromicum perstans: A rare skin condition of uncertain etiology, characterized by the gradual appearance of asymptomatic, blue-gray macules and patches, often on the face, neck, and upper trunk.