Depigmentation therapy for vitiligo
What is vitiligo?
What is depigmentation therapy?
Depigmentation therapy refers to medical treatments that remove skin pigmentation causing contact leukoderma. Depigmentation therapy is used in someone that has widespread, but incomplete, vitiligo on the face and/or other sites, in an attempt to improve their appearance.
The most commonly used depigmenting agent is monobenzyl ether of hydroquinone (MBEH). If the patient cannot tolerate MBEH, or if treatment fails, combination therapies or other treatments may be considered.
Who is suitable for depigmentation therapy?
Depigmentation therapy may be considered in the management of treatment-resistant vitiligo affecting more than 50% of the body surface area or affecting cosmetically sensitive, exposed body sites.
Informed consent for treatment with depigmentation agents
Prior to starting depigmentation therapy, the patient should understand:
- The permanent nature of the treatment
- The need for lifelong, strict sun protection to maintain benefits and reduce the risk of sun damage including skin cancer.
- The slow response to treatment and need for ‘touch–up’ sessions
- The potentially high cost of treatment
- Common and uncommon side effects and safety issues
- Risk that repigmentation will be patchy and incomplete
- Psychosocial and cultural issues that may arise from change in skin colour.
Patients should be given the opportunity to discuss treatment options with their family and friends.
Monobenzyl ether of hydroquinone
MBEH or monobenzone is the most commonly used depigmenting agent used in vitiligo. It is the only depigmentation treatment for extensive vitiligo that has been approved by the FDA (Food and Drug Agency, United States of America).
MBEH is a derivative of hydroquinone. Unlike hydroquinone, it almost always causes irreversible depigmentation, as it results in death of melanocytes (the cells that make skin pigment or melanin).
MBEH is available as a 20% cream, although it may be formulated up to 40% for difficult areas such as the elbows and knees. In the US, it is available as Benoquin® 20% cream. MBEH is not approved by Medsafe for use in New Zealand but may be obtained by medical practitioners from the manufacturer under Section 29. The full cost of the treatment must be paid by the patient.
Adverse reactions from MBEH are mostly mild.
- Transient irritation: stop treatment if burning sensation is severe.
- Contact irritant dermatitis (blistering, scaling, dry skin, swelling of treated sites): stop treatment and apply topical corticosteroids to affected areas. When the dermatitis subsides, consider using a weaker strength of MBEH.
- Less often, sensitisation or allergy to MBEH causes contact allergic dermatitis: stop treatment permanently and apply topical corticosteroids to affected areas.
- Loss of colour (leukoderma) at sites away from the area of application of the cream.
- Exogenous ochronosis (ashy brown pigmentation) after prolonged use of MBEH may include pigment deposition in the conjunctiva and cornea of the eyes.
- There is no safety data available for use of MBEH in women who may be pregnant or breastfeeding.
- Safety of MBEH in children below 12 years of age has not been established.
How do I use monobenzyl ether of hydroquinone?
- Tolerance to MBEH should be tested prior to commencing treatment on facial skin. Apply MBEH cream once daily for two weeks to a small area, such as the inner upper arm, then increase to twice daily.
- If tolerated, a thin layer of MBEH cream should be rubbed in twice daily to the pigmented areas to be lightened.
- Do not apply the cream to the eyelids or mucosal surfaces.
- Avoid sun exposure at all times to prevent the colour returning in patches.
Depigmentation is usually achieved after 1–4 months, however it may take up to 12 months for complete depigmentation of a particular site.
Treatment should be discontinued if the desired results are not achieved after 4 months of use. Once the desired degree of depigmentation is achieved, the cream may be applied intermittently to maintain this, usually twice a week.
Following treatment, the white skin will be sun sensitive lifelong. Apply SPF50+ broad-spectrum sunscreen to all white skin at least daily.
Monomethyl ether of hydroquinone
Monomethyl ether of hydroquinone (MMEH) is also known as 4-methoxyphenol, mequinol, or p-hydroxyanisole.
- MMEH has similar melanocytotoxic properties to MBEH.
- MMEH is usually compounded as a 20% cream.
- MMEH is applied in a similar manner to MBEH.
- Compared to MBEH, MMEH takes longer to achieve depigmentation, usually between 4 and 12 months.
- Skin irritation from MMEH is less common and less severe than with MBEH.
Phenol is relatively inexpensive. It has been traditionally used for deep chemical peels. Phenol is toxic to melanocytes, and prevents them from synthesising melanin. High-dose phenol (eg 88%) is also systemically toxic and must not be applied to large areas. It must be used very cautiously because it can cause severe chemical burns, heart arrhythmias and other dangers.
Phenol is used to treat small areas of persisting pigment in vitiligo, i.e. <20% of the face or neck area. For safety, use only 0.5-1 ml per session and the application duration should be no longer than 60 minutes. Phenol must be applied by an experienced physician.
- Cleanse the skin with alcohol
- Apply a cotton swab moistened with phenol to treat small areas until frosting is achieved.
- Maximum permissible amount per session is 1 ml.
- A burning sensation lasts about a minute, and gradually decreases in intensity over minutes to hours.
- Two treatments given 6 weeks apart are usually sufficient.
- Post-procedure care includes normal saline soaks and mild-moderate topical corticosteroids.
Side effects and risks of phenol include:
- Dyschromia (irregular pigmentation/depigmentation)
- Localised or disseminated herpes simplex virus infection. Anti–viral prophylaxis with aciclovir should be considered.
- Corrosion of any tissue it comes in contact with, by inhalation, ingestion, or direct skin contact.
- The 88% concentration rapidly coagulates the epidermis and thereby prevents it own percutaneous penetration, as compared to the traditional 40-50% phenol peels.
- Systemic toxicity results in cardiovascular shock, cardiac arrhythmias, bradycardia, and metabolic acidosis. These have been reported within 6 hours of peeling procedures with phenol.
Q-switched lasers, such as the ruby (694 nm), alexandrite (755 nm) and Nd:YAG (532 nm and 1064 nm) may be used alone or in combination with topical depigmenting agents such as MBEH or MMEH. These lasers work as depigmenting agents by selectively destroying melanin and melanin-bearing cells.
The main disadvantages of lasers in depigmentation therapy are:
- High cost
- Potential need for local anaesthetics due to pain
- Possible treatment failure
- Recurrence of pigmentation.
Cryotherapy with liquid nitrogen is a cost-effective permanent depigmenting treatment when rapid depigmentation of a small area is desired. It is simple, easy for an experienced physician to perform, and only requires a short preparation time. Melanocytes are exquisitely sensitive to cryodamage compared to keratinocytes and cryotherapy can result in permanent loss of colour (depigmentation) after treatment.
- Single 10-20 second freeze-thaw cycles are recommended, although one study has used two freeze-thaw cycles.
- Various techniques are described, including the use of a cryoprobe held approximately 40mm from the skin.
- Best cosmetic results are usually observed 4 weeks after cryotherapy.
- The procedure may need to be repeated at 4-6 week intervals for partially depigmented lesions until complete depigmentation occurs.
The disadvantages of cryotherapy include:
- It is unsuitable for large pigmented areas
- Dyschromia (irregular pigmentation/depigmentation)
- Recurrence of pigmentation
- Scarring (rare).
There are some reports that MBEH or MMEH combined with a topical retinoid such as tretinoin may overcome treatment resistance and enhance treatment efficacy. Retinoids help by inhibiting the melanocyte enzyme glutathione S-transferase.
Other potential depigmentation treatments
Imatinib is a medication used for chronic myeloid leukaemia, where depigmentation of the skin has been reported as a side effect within 4-12 weeks of receiving this medication. The suggested mechanism of action is that imatinib mesylate, a tyrosine kinase inhibitor, interferes in the production of melanin.
Imiquimod is an immune response modifier, used most commonly in the treatment of superficial skin cancers and genital warts. One of the side effects of treatment is sometimes permanent hypopigmentation, which may occur after 3 months of treatment. The postulated mechanism of action is that imiquimod can induce apoptosis of melanocytes.
Diphencyprone, also called diphenylcyclopropenone, is used in dermatology to treat conditions with altered immunological states, such as alopecia areata. Diphencyprone solution has been noted to sometimes result in hypopigmentation or complete depigmentation on treated areas, possibly due to its immunomodulatory effects. The onset of depigmentation is reported to occur after 10 months, and can occur even with concentrations as low as 0.0001%.
A number of phenolic compounds, including hydroquinone in concentrations higher than 4%, 4-ethoxyphenol, and 4-methylcatechol, are being tested for their depigmenting effects in animals, and appear promising. There is some suggestion that IFN-γ, busulfan and some melanoma vaccines (immunotherapy) have depigmenting activity.
Herbal products and depigmentation
The most common herbs used by traditional healers for voluntary depigmentation in Africa are:
- Brillantaisia cicatricosa Lindau (Acanthaceae)
- Chenopodium ugandae (Aellen) Aellen (Chenopodiaceae)
- Dolichopentas longiflora Oliv. (Rubiaceae)
- Protea madiensis Oliv. (Proteaceae)
- Sesamum angolense Welw. (Pedaliaceae).
- Ethanolic extracts of the leaves of Myrica rubra.
In vitro studies have indicated that these herbs may have effects on the production of melanin by melanocytes. This represents a potential area for future studies.