Patch

What is it?

A patch is essentially a large macule - a flat area of skin that has a different color than the surrounding skin but feels smooth when touched. The main difference between a patch and a macule is size: patches are larger than 1 centimeter (about the size of a fingernail or bigger). Like pressing a large stamp on paper, you can see the color difference but the surface remains flat.

What does it look like?

Patches appear as:

• Large flat areas of color change, bigger than your fingernail
• Can be as large as your palm or even cover entire body regions
• Various colors: white (vitiligo), brown (melasma), red (port-wine stains), purple, or tan
• Smooth surface with no elevation or depression
• Borders can be well-defined or blend gradually into normal skin
• Shape can be round, oval, irregular, or geographic (map-like)

Where does it appear?

Patches can develop anywhere:

• Face: Port-wine stains, melasma, large birthmarks
• Trunk: Vitiligo, tinea versicolor, morphea
• Back: Large café-au-lait marks, Becker's nevus
• Multiple areas: Vitiligo can affect face, hands, and body
• Sun-exposed areas: Large age spots (solar lentigines)
• Anywhere: Drug reactions, post-inflammatory changes

Associated features

Patches may be accompanied by:

• No symptoms (most common)
• Multiple patches that may merge together
• Gradual spreading over months or years
• Color changes with sun exposure or seasons
• Hair color changes within the patch (lighter or darker)
• Family history of similar patches
• Patches that appear at sites of skin injury (Koebner phenomenon)

When to see a doctor

Seek medical attention for:

• Rapidly spreading white patches (possible vitiligo)
• New large brown patches in adults
• Patches that are growing or changing
• Red or purple patches that don't blanch (turn white) with pressure
• Patches with irregular borders or multiple colors
• Any patch accompanied by other symptoms
• Cosmetic concerns affecting quality of life