Heal House Vitiligo Research 29 · Letter
How to distinguish nevus depigmentosus from segmental vitiligo?
Excimer stamp test distinguishing between nevus depigmentosus and segmental vitiligo
Final review
In short
Nevus depigmentosus is a congenital white spot, while segmental vitiligo is a disease where pigment cells disappear and can spread. The 'stamp test,' where an excimer laser is lightly applied like a stamp, can differentiate the two without difficulty.
"My child has a white spot on their body—is it just a mole or vitiligo?" Parents often ask this with concern. In fact, 'nevus depigmentosus,' which is present from birth, and 'segmental vitiligo,' which can spread, look very similar on the surface. However, the future course and treatment approach for the two conditions are different. Therefore, accurately distinguishing between them is important. So I organized and introduced a simple method that can be performed in the clinic.
Q1 How are nevus depigmentosus and segmental vitiligo different, and how can a stamp test tell them apart?
The biggest difference is whether pigment cells remain. Nevus depigmentosus is a white spot present from birth. The pigment cells themselves remain, but their function is weak. It only grows as the body grows and does not spread to new areas. In contrast, segmental vitiligo is a disease in which pigment cells disappear due to an immune response. It can spread over time, and there is potential to restore color with phototherapy or laser. The stamp test is a method of briefly applying an excimer laser to the white spot once, like stamping. It examines how the skin at that site reacts. Nevus depigmentosus, which retains pigment cells, and vitiligo, which does not, respond differently to this stimulus. Thus, without complex tests, you can obtain clues to distinguish between the two conditions.
Closing remarks
Accurately distinguishing between these two similar conditions early on can reduce unnecessary worry and ineffective treatment. If it is nevus depigmentosus, you can be reassured and simply observe. If it is segmental vitiligo, you can start treatment promptly before it spreads. Since it is a method that can be performed right in the clinic without special equipment, I find it useful when differentiating white spots.
