DR WU SKIN CLINIC
Pigmentation
Pigmentation disorders, either hypo or hyperpigmented, used to be one of the most disturbing dermatological problems. In the last ten years, I had been trying to have an reasonable method based on basic research to treat pigmentary disorders. In the process, I found current knowledge about pigmentary disorders had some pitfalls. There were lots of research papers that described the effectiveness of various lasers in treating pigmentation disorders. However, there were few integrated knowledge in the sea of literature. Before I describe how I treat these patients, I should clarify my own integrated theory underlying my clinical practice.
1. I think the selective photothermolysis, the basic theory underlying modern laser treatment, is correct in theory but not always true in practice. The theory focused on "small object need small pulse duration" to reduce the thermal spillage to surrounding tissue. It is true but neglects the importance that we are dealing with living cells. For example, heat applied to the melanosome with nanosecond pulse duration had not much difference with the longer pulse duration targeting the whole cells when the cells are finally killed. That is why long-pulsed Alexandrite laser had the same effect but better side-effect profile in comparing the Q-switched Alexandrite in treating freckles. (1)
2. Laser, intense pulse light, cryotherapy, electrodessication achieve the clinical effect by permanently kill pigmented cells. Basically, pigmentary disorders occur due to the DNA damage, most from sunlight, to the genes involving in pigmentation process within cells. Laser can not repair the damaged DNA that result in abnormal pigmentation. Lasers or other forms of energy treating pigmentary disorders by killing the abnormal pigmented cells selectively. When the abnormal cells were killed, the pigmentation disorder was cured. That is why I prefer to use high-energy laser. Some people claim the effectiveness of the low-fluency laser like ND-YAG lasers in treating pigmentary disorder like melanoma. However, these treatment had no curing effects and frequently result in side effect after repeating and repeating the procedures. That is also the reason I am an opponent to the advertised "laser toning" effect by current picosecond lasers. To have an effect but avoiding the nonselective damage from photoacoustic effect of picosecond laser, these lasers have to be given in the energy lower than that required to kill cells. The melanosome is thus damaged but the cells not killed, so the result hypopigmentation effect is only transient but not cure the problem. If transient hypopigmenation is what people wished, topical hydroquinone is a better option and no lasers is needed.
3. The hyperpigmentation disorders are not always a keratinocyte-mleanocytes problem. This is my theory that took lots of painful experience to have. Although it is contrary to most dermatologists and textbooks in pigmentation, my hypothesis does have solid supportive evidence, although I won't discuss it here.
How I treat pigmented disorders.
1. Freckles, lentigo (distinct blackish spots on face with clear margin): I use intense pulse light, the M22 from Lumenis, and usually achieve clearing permanently in single treatment. I sometimes used ND-YAG laser at 532 nm which is suitable for few spots and have the same result but more post inflammatory hyperpigmenation in comparison with IPL.
2. Thin seborrheic keratosis (face): I still prefer intense pulse light. Single treatment was often what needed for permanent removal. However, the treatment usually left post inflammatory hyperpigmentation that need few months to subside.
3. Thick Seborrheic keratosis: cryotherapy, Carbon dioxide laser was need. still single treatment is needed.
4. Melasma: I think melasma is the most difficult condition to treat. For many years, I had found superficial dermabrasion is the only way to permanent remove melasma.