Epidermal

• Well-defined border
• Dark brown colour
• Appears more obvious under black light
• Responds well to treatment

Dermal

• Ill-defined border
• Light brown or bluish in colour
• Unchanged under black light
• Responds poorly to treatment

Mixed

• The most common type
• Combination of bluish, light and dark brown patches
• Mixed pattern seen under black light
• Partial improvement with treatment