Dr. Zhou
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National report — Treatment of dermal pigmentation disorders requires patience, according to Youwen Zhou, M.D., Ph.D., F.R.C.P.C., assistant
professor in the division of dermatology at the Vancouver General Hospital and the University of British Columbia in Vancouver,
Canada.
"Epidermal pigmentation disorders respond very well to lasers and intense pulsed light-based technologies. However, dermal
pigmentation disorders are completely different," Dr. Zhou tells Dermatology Times. "They do not respond to such therapies. Topical preparations are used for depigmentation."
In diagnosing melanin pigmentation disorders, dermatologists should perform a comprehensive assessment to rule out malignancies
and precursors to malignancies, as well as systemic diseases that require intervention. Onset of the disorder is important
information in the clinical history of the pigmentation disorder, because disease onset indicates whether the disorder is
likely to be developmentally programmed (congenital) or acquired.
In assessing the events preceding the onset of the pigmentation disorder, the dermatologist should ask whether there was inflammation,
whether the skin had been exposed to chemical or physical factors, and whether the patient had received any medications that
might cause pigment deposition.
Also, did the patient receive any previous treatments for the pigmentation disorder, and if so, what was the response to treatment?
Clinical examination
In assessing the condition, physicians should consider the distribution of lesions, whether they are generalized or localized,
and the appearance of the individual lesions, Dr. Zhou says.
"It is crucial to focus on the borders of individual lesions," he says. "Are the lesions clearly defined or poorly defined?"
Localized lesions that are poorly demarcated are likely to be dermal in origin.
"The most common pigmentation disorders that can be treated easily in a clinic are sun exposure and aging-related pigmentation
disorders such as ephelides and solar lentigos," Dr. Zhou says. "Another common pigmentation disorder that is easily treated
is melasma."
Patients also seek treatment for flat seborrheic keratoses (SK) or deep-penetrating nevi (DPN) in the early stages, for mucosal
melanosis, and for caf-au-lait macules (CALM).
"Epidermal pigmentation disorders generally respond to destructive therapies, especially QS laser therapies," Dr. Zhou notes.
"Intense-pulsed laser is less effective, but there is less downtime."
Ephelides
The most common localized pigmentation disorders affecting the epidermis are ephelides, or freckles. Ephelides appear as macular
brown pigmentation in sun-exposed areas, usually on the face. They are more common in light-skinned individuals, and the tendency
to have freckles is a heritable condition. The degree of pigmentation changes according to UV exposure, with freckles usually
darkening in the summer and lightening in the winter.
QS lasers and intense-pulsed laser treatments are effective for depigmentation, and ephelides occasionally respond to topical
depigmentation preparations. Whether treatment is considered is a culturally based decision.
"In general, east Asians are more likely to seek treatment for this condition," Dr. Zhou says.
Solar lentigos
Other common epidermal lesions, larger and darker than ephelides, are solar lentigos, also known as actinic or senile lentigo.
These lesions range in size and shape from macules to thin papules or plaques. Solar lentigos are induced by chronic sun exposure.
"Patients usually develop solar lentigos starting in the 20s, and the lesions increase with advancing age," Dr. Zhou says.
"They are more common in East Asians than Caucasians."
"In my practice the most effective treatment for solar lentigo is Q-switched laser therapy," Dr. Zhou remarks. "Cryotherapy
in dark-skinned individuals may cause permanent hypopigmentation and should be avoided."
Mucosal melanosis
Mucosal melanosis arises from increased melanin in the mucosal squamous cells. There is no significant increase in the number
of melanocytes.
Patients with mucosal melanosis have brown, well-demarcated macules that usually appear on the lips or labial mucosa. In most
cases these lesions are benign, but clinical monitoring is essential in order to rule out melanoma.
QS lasers and cryotherapy are effective treatment options. Follow-up is necessary, and biopsy should be performed if the macules
recur.
Dermal pigmentation disorders
Dermal pigmentation disorders, such as melasma, arise from increased melanin in the epidermis and increased free melanin and
melanophages. The pigmentation occurs deeper in the skin, and has a less distinct border. The pigmentation is brown, but the
color may be mixed with gray or blue. In general, dermal pigmentation disorders are difficult to treat.
"Bleaching creams are the most frequently used therapies, but the efficacy is less than ideal," Dr. Zhou says. "Better therapies
are needed."
Melasma
Melasma is a common condition, occurring in up to 10 percent of women. The incidence of melasma is higher in Asians and darker-skinned
individuals than in Europeans and lighter-skinned individuals. Melasma affects both sexes, but is more common in women than
in men. The disease mechanism is unknown, but probably involves multiple factors, including genetic predisposition, hormonal
stimulation and UV exposure.
There is no curative therapy for melasma. Patients with melasma should avoid conditions that trigger melasma, such as UV exposure.
Strict sun protection is necessary.
"Skin-bleaching creams may be useful, and maintenance therapy is usually required," Dr. Zhou says. "There are no other therapies
that are safe and effective for melasma ... cryotherapy and laser therapies should be avoided."
Post-inflammatory hyperpigmentation
A dermal disorder that commonly affects darker skin is post-inflammatory hyperpigmentation, or PIH. The underlying mechanism
is unclear, but it probably involves inflammatory mediators such as PGE2 and leukotriene C4 acting through a G-protein coupled
receptor pathway.
The causes of PIH and the clinical presentation vary. Patients with PIH should avoid sun exposure.
"Therapy for PIH is often not necessary, but depigmentation topical preparations may be helpful," Dr. Zhou says.
Depigmentation therapies
Tyrosinase is the key enzyme regulating the synthesis of melanins from tyrosine. All bleaching agents currently used for treatment
of dermal pigmentation disorders target tyrosinase directly, either by transcriptional inhibition of the tyrosinase gene or
by post-translational inhibition of tyrosinase protein activity.
"Agents with different mechanisms of action may offer novel therapeutic options in the future," Dr. Zhou says.
Disclosure: Dr. Zhou reports no conflicts of interest relevant to this article.
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