Abstract
Background: Although a variety of topical treatments have been used for skin hyperpigmentation, the effectiveness is variable after prolonged treatment.
Objective: One hundred and thirty six Oriental patients followed up for more than 12 weeks were analyzed in this study.
Methods: The protocol was composed of two steps: a bleaching step (2-6 weeks) and a healing step (2-6 weeks). 0.1-0.4% all-trans retinoic acid aqueous gel was originally prepared and applied concomitantly with hydroquinone, lactic acid ointment for bleaching. After obtaining sufficient improvement of the hyperpigmentation, corticosteroid was topically applied with hydroquinone and ascorbic acid in the healing step. Improvement was evaluated with a narrow-band reflectance spectrophotometer.
Results: The results were successful in more than 80% of senile lentigines and postinflammatory hyperpigmentations, especially on the face. Sixty percent of nevus spilus were also successfully treated.
Conclusion: Although transient adverse effects may be more severe, this strong bleaching protocol enables an improvement of a variety of hyperpigmented lesions including nevus spilus with a higher success rate and a shorter period of treatment than conventional protocols.
 
Introduction
   All-trans retinoic acid (atRA; tretinoin) has been topically used for the treatment of acne, photodamaged skin and hyperpigmentation as well as before and after skin resurfacing such as carbon dioxide laser and chemical peeling101,102. Kligman’s well-known regimen1 and several modifications2, 3 have been widely used as a topical bleaching formula for two decades and a number of products based on them are commercially available. However, the improvement is variable and sometimes limited or unrecognizable, and it usually takes a prolonged time of treatment.
   The authors proposed a new bleaching protocol with a high concentration of atRA aqueous gel and have treated over 300 Oriental patients with skin hyperpigmented lesions such as senile lentigines, postinflammatory hyperpigmentation, melasma, and nevus spilus. These skin lesions with hyperpigmentation have been treated with a variety of therapies including laser and chemical peeling, and except with senile lentigines, the results have not been very satisfactory4, 5, 6,100. The management of postoperative hyperpigmentation is quite important for dermatologic or plastic surgeons performing facial skin resurfacing. Furthermore, there have been no reports indicating the effectiveness of topical treatments on nevus spilus for which there is no standard therapy to date (6,100). Although our protocol requires two steps (a bleaching step and a healing step), and transient adverse skin reactions associated with this protocol may be more severe, it enables an improvement of a variety of hyperpigmented lesions including nevus spilus with a higher success rate and a shorter period of treatment than those of conventional protocols.

 Materials and Methods
Preparation of Ointments: AtRA aqueous gels (atRA gel) with 3 different concentrations (0.1, 0.2, and 0.4 %) were originally prepared at the Department of Pharmacy, University of Tokyo. The precise regimen of 0.1-0.4% atRA aqueous gel for 1000g was as follows: atRA (Sigma Chemical, St. Louis, MO) 1-4g, Carbopol 940 (Goodrich Chemical, Hounlow, UK) 10g, polyoxyethylene oleyl ether (Kao, Tokyo, Japan) 20g, methyl p-hydroxybenzoate (Wako Pure Chemical Industries, Osaka, Japan) 0.26g, propyl p-hydroxybenzoate (Wako Pure Chemical Industries, Osaka, Japan) 0.14g, 10% sodium hydroxide aqueous solution 6ml, purified water ad.1000g. An ointment including 5% hydroquinone and 7% lactic acid (HQ-LA ointment) and one including 5% hydroquinone and 10% l-ascorbic acid (HQ-AA ointment) were also prepared at the Department of Pharmacy, University of Tokyo. Plastibase? (petrolatum polyethylene ointment base, Taisho Pharmacology, Osaka, Japan) and hydrophilic ointment were used as the ointment bases of the HQ-LA ointment and HQ-AA ointment, respectively. Because all ointments (atRA gel, HQ-LA ointment, and HQ-AA ointment) are pharmacologically unstable, fresh ointments were prepared at least once a month and stored in a dark and cool (4?C) place.
Patients: Each ointment was topically applied under signed informed consent in more than 300 patients with hyperpigmented skin lesions. One hundred and thirty six patients, who had hyperpigmented lesions of which the relative melanin value (RMV; see below) were more than 30 and were followed up for more than 12 weeks, were analyzed in this study. All of them were Oriental: 128 Japanese, 3 Chinese, 3 Korean and 2 Indian. Clinical diagnoses of hyperpigmented lesions were classified into four categories; senile lentigines (SL), melasma (ML), postinflammatory hyperpigmentation (PIH), and nevus spilus (NS) which included caf? au lait spots. Patients with PIH of less than 6 months duration were excluded from this study. The age of patients varied from 4 to 88 years old (age=44.6±15.3; mean?S.D.), and 112 cases were female. The data of patients are summarized in Table 1. Some patients had hyperpigmented lesions and underwent the treatment on more than one part of the body, so that the total number of patients in the data is 146. The data were analyzed according to the clinical diagnosis and the sites of the skin lesions, and included 90 patients with SL (on the face in 61 patients, on the trunk in 3, on the upper extremities in 24, and on the lower extremities in 2), 10 patients with ML (on the face in all patients), 28 patients with PIH (on the face in 11 patients, on the trunk in 6, on the upper extremities in 7, and on the lower extremities in 4), and 18 patients with NS (on the face in 9 patients, on the trunk in 5, on the upper extremities in 2, and on the lower extremities in 2).

Treatment protocol: Our bleaching protocol is composed of two steps, a bleaching step and a healing step. In the bleaching step, the pigmentation is aggressively treated, and transient adverse skin effects such as erythema and irritation are usually observed. Once satisfactory improvement is obtained, the healing step is started in order to reduce the erythema and inflammation. In some cases, a pretreatment was conducted before the bleaching step.
1) pretreatment: The application of HQ-LA ointment (HQ-AA ointment in some cases) to the skin lesions twice daily for several weeks was recommended to those who wanted to start the bleaching treatment in several weeks for personal reasons. In summer, every patient was advised to have only a pretreatment with HQ-LA ointment until September to avoid strong UV irradiation during the bleaching step. In the daytime, a broad-spectrum sunscreen cream was always concomitantly applied with the other ointments throughout the treatment period.
2) bleaching step: AtRA gel and HQ-LA ointment were applied to the skin lesions twice a day. Initially, the concentration of atRA was determined according to the location of the skin lesions: 0.1% atRA gel for the face, 0.2% for the trunk or upper extremities, and 0.4% for the lower extremities. Patients were requested to visit our hospital at 1, 2, 4, 6, 8, 12, and 16 weeks after starting this treatment. When the appropriate skin reaction was not observed at 1 week, the concentration of atRA was changed (usually to a higher one). In most cases, it took 2 to 6 weeks to finish this step.
   If a satisfactory improvement (= 80% improvement of relative melanin value; see below) was not obtained after 8 weeks’ continual treatment of atRA gel and HQ-LA ointment, the treatment was discontinued. In those cases, the second treatment was started after a 2 to 3 months interval of atRA gel application. Throughout this interval, HQ-LA (or HQ-AA) ointment was recommended as a pretreatment for the 2nd treatment, which is the same protocol as the first treatment..
3) healing step: After sufficient improvement of the hyperpigmentation was obtained, the application of atRA gel and HQ-LA ointment was discontinued, and topical application of corticosteroids (0.12% betamethasone valerate or 0.3% prednisolone butylacetate ointment) and HQ-AA ointment (HQ-LA ointment in some cases) for as short a time as possible (usually 1 to 3 weeks) was started to reduce the reactive erythema and inflammation. After the erythema was reduced to some extent, the application of corticosteroid was discontinued and only HQ-AA ointment was continuously applied. In cases in which erythema was not reduced after a few weeks’ application of corticosteroid and HQ-AA ointment, HQ-AA ointment was also discontinued for a few weeks. In some cases in which reactive erythema was not so severe, this step was omitted.
4) Post-treatment maintenance: After the bleaching and healing steps were finished, the continual application of HQ-LA or HQ-AA ointment for several months was advised for post-treatment maintenance in some cases including all cases with NS. In cases with NS, when clinical signs of recurrence of pigmentation were observed, atRA gel was also used as maintenance or the 2nd treatment was started.

Evaluations of results:
1) Spectrophotometry: As an objective measurement of the color of the designated lesion and surrounding normal skin, a narrow-band reflectance spectrophotometer (Mexameter MX 16, COURAGE+KHAZAKA electric GmbH, K?ln, Germany) was used at each clinical visit. The overall results were objectively evaluated by the melanin and hemoglobin values measured with Mexameter?. A measuring probe with a measuring area of 5mm diameter emits light of 3 pre-defined wavelengths (568 nm: green, 660 nm: red, and 880 nm: infrared), and measures the light reflected by the skin. The melanin value is measured by using 2 wavelengths (660nm and 880 nm) to achieve different absorption rates by the melanin granules. For the hemoglobin measurement as well, 2 wavelengths (568 nm and 660 nm) are used. The melanin and hemoglobin values are calculated as follows:
Melanin value = 500/ log 5 x (log infrared-reflection/ red-reflection + log 5)
Hemoglobin value = 500/ log 5 x (log red-reflection/ green-reflection + log 5)
Each spot was measured 3 times and the average of 3 measured values was calculated. The difference in the absolute melanin and hemoglobin value between a skin lesion and the surrounding normal skin is referred to in this paper as the relative melanin value (RMV) and the relative hemoglobin value (RHV) of the skin lesion, respectively. RMV and RHV indicate the intensity of pigmentation and erythema relative to the surrounding normal skin, respectively. A negative RMV means that the measured spot is lighter than the control. RMV was compared between before and after the 1st treatment, and the results were classified into the 4 following grades: “excellent”, final RMV was 5 or less; “good”, final RMV was reduced to less than 20% of the RMV before treatment; “fair”, final RMV was reduced to less than 60% of the RMV before treatment; “poor”, final RMV was more than 60% of the RMV before treatment. The absolute melanin value of normal skin in Japanese and the RMV of hyperpigmented lesions are usually 460-500 and 20-120, respectively. Five or less of RMV is difficult to clinically recognize.
2) Statistics: The results were analyzed according to the diagnosis and locations of the skin lesions. Significant differences were sought using Kruskal-Wallis test. Differences were considered significant when H values > x2(0.95).

 Results
In general, erythema was seen in a few days, followed by continuous scaling during the first week25. Erythema and scaling was usually continuously seen throughout the bleaching step. Formation of a thin crust was also seen in some cases during the second week. After the thin crusts came off, the elimination of pigmentation was usually obtained. An improvement of hyperpigmentation was obtained after a bleaching step of 2-4 weeks in most cases with SL or PIH, while a somewhat longer period was usually required for NS. The second treatment was performed for further improvement in 19 cases (21.1%) with SL, 6 cases (60.0%) with ML, 1 cases (3.6%) with PIH, and 16 cases (88.9%) with NS.
The results of the treatment were evaluated with spectrophotometry and summarized in Table 2. Cases evaluated as “excellent” or “good” were referred to as successful in this paper and success rates were calculated as following: [number of “excellent” and “good” cases]/ [number of total cases].
In the cases with SL, 27 cases (23 cases on the face and 4 on the upper extremities) were evaluated as “excellent”, 47 cases (35 cases on the face, 2 on the trunk, and 10 on the upper extremities) as “good”, 13 cases (3 cases on the face, 1 on the trunk, 8 on the upper extremities, and 1 on the lower extremities) as “fair”, and 3 cases (2 cases on the upper extremities and 1 on the lower extremities) as “poor”. In the cases with ML, 2 cases were evaluated as “excellent”, 5 cases as “good”, 2 cases as “fair”, and 1 case as “poor”. In the cases with PIH, 10 cases (5 cases on the face, 2 on the trunk, 1 on the upper extremities, and 2 on the lower extremities) were evaluated as “excellent”, 14 cases (6 cases on the face, 3 on the trunk, 4 on the upper extremities, and 1 on the lower extremities) as “good”, 3 cases (1 case on the trunk, 1 on the upper extremities, and 1 on the lower extremities) as “fair”, and 1 case (on the upper extremities) as “poor”. In the cases with NS, 5 cases (3 cases on the face and 2 on the trunk) were evaluated as “excellent”, 6 cases (3 cases on the face, 1 on the trunk, 1 on the upper extremities and 1 on the upper extremities) as “good”, 5 cases (3 cases on the face, 1 on the trunk, and 1 on the upper extremities) as “fair”, and 2 cases (1 case on the trunk and 1 on the lower extremities) as “poor”.
    The success rate for SL was 82.2% (95.1% for SL on the face and 58.3% for SL on the upper extremities). The success rates for ML, PIH, and NS were 70.0%, 85.7%, and 61.1%, respectively. Significant differences were not seen among the four diagnosis (H value= 2.67, x2(0.95)=7.81). On the other hand, classified according to the locations of the skin lesions, there was a significant difference between four locations (H value= 12.44, x2(0.95)=7.81). The success rates for face, trunk, upper extremities, and lower extremities were 90.1%, 71.4%, 60.1%, and 50.0%, respectively. The total success rate for 146 cases was approximately 80%.

Case Report

Case 1: A 54-year-old woman with a senile lentigine on her left cheek underwent combined topical applications of 0.1% atRA gel and HQ-LA ointment without a pretreatment (Fig.2A: before treatment). The initial reaction such as erythema and scaling was appropriate (Fig 2B: at 1 week), and at 2 weeks the hyperpigmentation had disappeared completely, despite the severe erythema and formation of a thin crust on the treated region (Fig. 2C: after a bleaching step of 2 weeks). AtRA-gel and HQ-LA ointment were discontinued and topical application of corticosteroid and HQ-AA was started. Corticosteroid was applied for 2 weeks (Fig. 2D: at 4 weeks). Four weeks after the discontinuation of corticosteroid, the erythema disappeared completely. (Fig. 2E: after treatment for 8 weeks). HQ-AA ointment was applied throughout the healing step for 6 weeks., and the final RMV after 8 weeks’ treatment was 4.3. The result was evaluated as “excellent”. The sequential data of spectrophotometry are shown in Fig. 2F. Although the extent of erythema seen at 2 weeks was nearly most severe among the cases we experienced, the time course of clinical changes of this case was typical in this treatment. The RMV and RHV before treatment were 166.7 and 46.0, respectively. RHV is generally positive in hyperpigmented lesions. During the bleaching step, RMV was considerably reduced, while RHV was increased as the inflammation progressed. During the healing step, RHV gradually decreased, while the improvement of RMV was maintained. RHV was reduced to even below the level before treatment. The final RMV and RHV after 8 week’ treatment were 4.3 and 18.8, respectively.

Case 2: A 60-year-old man with multiple senile lentigines on his bilateral cheeks underwent combined topical applications of 0.1% atRA gel and HQ-LA ointment without a pretreatment (Fig. 3A, 3B: before treatment). Appropriate reactions were seen during the 1st and 2nd week, and the healing step was started at 2 weeks. The hyperpigmentation and erythema had almost disappeared by the 8th week. Occasional application of atRA and HQ-LA ointment was done after treatment for maintenance (Fig. 3C, 3D: at 20 weeks). The RMVs of pigmented spots before treatment were 65.3 (left) and 52.3 (right), and the final RMVs after 8 weeks’ treatment were ?1.2 (left) and -4.0 (right), respectively. The result was evaluated as “excellent”.

Case 3: A 28-year-old man underwent a split-thickness skin graft from the medial aspect of the right upper arm to the face 3 years before his first clinical visit, and postinflammatory hyperpigmentation remained on the donor site of the graft (Fig. 5A: before treatment). Topical applications of 0.2% atRA gel and HQ-LA ointment were started without a pretreatment. On day 5 scaling was seen, and thereafter hyperpigmentation was reduced significantly. At 3 weeks the healing step was started, and the erythema was almost eliminated at 8 weeks. No recurrence was seen at 20 weeks. (Fig. 5B: at 20 weeks). RMV before and after treatment was 41.4 and 2.1, respectively. The evaluation of this case was “excellent”.

Case 4: A 16-year-old woman with congenital nevus spilus on the left cheek underwent combined topical applications of 0.1% atRA gel and HQ-LA ointment without a pretreatment (Fig. 6A: before treatment). The initial reaction such as erythema and scaling was appropriate, and thin crusts came off during the 2nd to 3rd weeks (Fig. 6B: at 3 weeks). The bleaching step was continued for 4 weeks, followed by a healing step of 4 weeks. The RMV before treatment was 41.7, and the RMV at 8 weeks was ?3.5 (Fig. 6C: at 8 weeks). Although HQ-LA ointment was continually applied after the treatment for maintenance, signs of recurrence were detected 6 weeks later. Therefore, atRA as well as HQ-LA ointment was applied once daily, and this maintenance was working well even 10 months later (Fig. 6D: at 12 months). The result was evaluated as “excellent”.

Case 5: A 61-year-old woman with nevus spilus on the left cheek, who had undergone cryotherapy with dry ice 4 times and dermabrasion 2 times resulting in no improvement, underwent combined topical applications of 0.1% atRA gel and HQ-LA ointment without a pretreatment (Fig. 7A: before treatment). The initial reactions such as erythema and scaling were appropriate, and the pigmentation was reduced significantly. As the erythema gradually reduced during the bleaching step in this case, the bleaching step was continued for 8 weeks, and no healing step was required (Fig. 7B: at 8 weeks). The RMVs before and after treatment were 72.3 and ?3.6, respectively. Although the HQ-LA ointment was continually applied after the treatment for maintenance, signs of recurrence of the pigmentation were observed one month after the cessation of atRA. AtRA as well as HQ-LA ointment was continually used for maintenance, and the pigmentation was controlled very well even 15 months later (Fig. 7C: at 15 months). The result was evaluated as “excellent”.

 Discussion
Characteristics of the present protocol
For bleaching, atRA and hydroquinone play essential roles in this protocol, while lactic acid and ascorbic acid were utilized supplementally. Although ascorbic acid is also known to have a depigmenting effect and fewer adverse effects than hydroquinone, its depigmenting ability is far less than that of hydroquinone8. It is clear that the same results can not be obtained from the single use of either atRA9 or hydroquinone10. Although hydroquinone was used also in the healing step, but the authors did not expect it to further improve pigmentation but to prevent postinflammatory hyperpigmentation and recurrence of pigmentation, thus maintain the level of improvement obtained in the bleaching step.
Based on our preliminary trials with several concentrations of atRA in several vehicles and the concomitant use of corticosteroid with atRA, we believe the critical points of this protocol are: 1) to use a high concentration of atRA “aqueous gel “and 2) to not use corticosteroid concomitantly with atRA. Various kinds of atRA gels with higher concentrations than those commercially available were originally prepared. 0.01 to 0.1% cream-base atRA (0.01-0.1% Retin-A?) has been widely used and the concentration of atRA in aqueous gel-base products is usually lower because of the higher permeability of the vehicle. The authors prepared 0.1-0.4% atRA using aqueous gel as a vehicle because of its higher permeability and economical benefits. We assume that 0.1% atRA aqueous gel corresponds to 0.3-0.4% atRA cream or hydrophilic ointment in terms of the efficiency of drug delivery. As atRA is pharmacologically unstable, its concentration in our vehicle is spontaneously reduced to 90% in 1 month (data not shown) even when stored in a refrigerator. Thus, it is necessary for new atRA gels to be prepared at least once a month.

Effectiveness on skin hyperpigmentation
The present results demonstrated that the effectiveness of the treatment varies according to the diagnosis and location of the lesions. Although statistical significance in the improvement scores was not detected, the success rates for SL and PIH were very high, especially for those on the face. On the other hand, the success rate for NS was approximately 60%. However, neither laser therapies nor any other therapies even combined with hydroquinone can treat NS very well, and the recurrence of pigmentation is also very common, suggesting that our bleaching protocol has potential as a therapy for NS.
    The location of the skin lesions is also quite important in this therapy. The success rate for the face was over 90%, while those for the trunk and upper extremities were 71.4% and 60.1%, respectively. Although the number of cases was small, the success rate for the lower extremities was only 50%. Statistical significance in the improvement scores was found between the face and upper extremities. The skin reactions to atRA are milder and slower on the trunk and extremities, especially on the lower extremities, than on the face. Differences in the permeability and vascularity of the skin, associated with the penetration and resorption of the reagent and wound healing, are suspected to be the main reasons for the differences in the skin reactions. Therefore, higher concentrations of atRA were utilized in this protocol for the trunk and extremities; 0.2% atRA gel for the trunk and upper extremities, and 0.4% for the lower extremities, leading to much better clinical results than those with 0.1% atRA gel.

Mechanisms of action of atRA and hydroquinone
The mechanisms by which atRA and hydroquinone act in the combined protocols(1,2) such as in Kligman’s regimen and ours is still to be elucidated. Although a number of studies have been performed concerning the effects of atRA on skin in vivo or with keratinocytes and other cells in the skin in vitro, there are some contradictory results the reasons for which remain unknown11, 12, 16. Although it is reported that even the topical application of atRA alone has a clinically depigmenting effect 9, 13, 14, the suppressive effects of atRA on melanocyte growth and melanogenesis have not been established in vitro15 (Yoshimura, in preparation). AtRA promotes the proliferation of keratinocytes in vivo, and hyperplasia of the epidermis is a characteristic change after the topical application of atRA16. However, the promotion of keratinocyte growth is variable in vitro12. It was reported that atRA can promote collagenesis and wound healing17, 18,103. On the other hand, it is known that skin becomes atrophic after the application of corticosteroid19, 20 and that corticosteroid suppresses collagenesis and wound healing21. Thus, corticosteroid appears to be antagonistic to retinoids in some aspects18, 19, 20, 22.
    Corticosteroids are known to have a depigmenting effect with single use23, and this is one of the reasons why Kligman employed corticosteroid in his regimen1. However, based on our preliminary clinical trials and the differences in the results of the present report and those of other conventional reports in which atRA and corticosteroids were concomitantly used, we believe that corticosteroids suppress the beneficial effects of atRA in the depigmenting treatment and should not be used concomitantly with atRA. Also, in our experience, peeling such as that by carbon dioxide laser followed by topical hydroquinone treatment could not lead the same results, suggesting that the scaling or peeling effect is not the primary cause of the effectiveness of atRA in this treatment. Taken together, it is speculated that the strong promotion of keratinocyte proliferation and wound healing is most likely to be the roles of atRA in this depigmenting protocol. The promotion of permeability induced by repeated scaling and mucinous accumulation in the extracellular spaces may be a supplemental benefit of atRA in this treatment24.

Side Effects
   Adverse effects on the skin such as irritation and erythema may be seen at a higher rate in this protocol than in conventional ones because of the high concentrations of atRA25. Indeed, 10-15% of the patients did not complete the treatment, although accurate assessment of the number of dropouts was difficult because there were some patients who did not revisit the hospital for unknown reasons. Although it has been considered that high concentrations of atRA accentuate irritation without a corresponding gain in effectiveness1, 18, our protocol with higher concentrations of atRA aqueous gel lead to much better objective and clinical results and subjective satisfaction than the lower concentrations. These differences may be partly derived from racial differences in the subjects.
    It is known that continuous application of atRA leads to tolerance in the treated skin27. After a few weeks’ treatment, the side effects such as erythema and irritation decrease with time even during the bleaching step. Indeed, it was not necessary to conduct the healing step in some patients such as case #6. Also, we have some patients who are using 0.4% atRA gel on the face for maintenance without any adverse skin effects. Although the mechanism by which tolerance is obtained and whether the beneficial effects of atRA are also lost have not been established, the increased tolerance is the reason why we usually use the higher concentration of atRA gel in the 2nd treatment.
    Another possible side effect is PIH induced by the skin inflammation of the bleaching step. During the healing step, erythema is gradually reduced, but PIH occurred in some cases. In most of those cases, PIH gradually disappeared in a couple of months. Otherwise, it can be treated by the present treatment. The skin color of Oriental patients may be one of the factors of PIH.

Recurrence
    In cases with SL or ML, which were followed up for more than 6 months, recurrence of the lesion was occasionally observed, but the number of such cases was small. Recurrence was seen several months after cessation of the treatment. On the other hand, recurrence was rarely seen in cases with PIH. Among cases with NS, nearly 80% exhibited some signs of recurrence a couple of months after they stopped the treatment. However, recurring pigmentation was usually reduced or eliminated by the 2nd treatment in cases in which the 1st treatment was effective. Therefore, continual treatment with atRA or hydroquinone would be recommended in NS cases even when the result of the 1st treatment is “excellent”. Only for pregnant patients with NS, it could be a problem to continue treatment with atRA which is known to be a possible teratogen28.

Indication of the treatment and application to combination therapies
   The present protocol can be applied to almost any kind of skin lesions with hyperpigmentation, preferably when the intensity of pigmentation is high, for example, when the RMV is over 30. Taking into consideration the fact that the reactive inflammation accompanying the bleaching step possibly induces PIH during the healing step, any other mild treatment could be recommended for lesions the pigmentation of which is very weak, for example when the RMV is less than 15. It should be noted that our bleaching protocol is not very effective for lesions with hyperkeratosis. In such cases, other treatments such as liquid nitrogen and carbon dioxide laser should be applied prior to the bleaching step. Possible side effects during the bleaching step should be explained well and the firm intention of the patients to undergo aggressive treatment should be confirmed before starting the bleaching step as with any other surgery or chemical peeling. Finally, it is emphasized that repeated treatments with this protocol can remarkably improve photoaged skin not only in terms of skin color but also in skin texture and elasticity, eliminating surface roughness and fine wrinkles.

Conclusions
The authors proposed a strong bleaching protocol in which atRA aqueous gels were used at high concentrations and corticosteroids were minimally used. Although reactive adverse effects may be more severe, the present protocol enables improvement of hyperpigmentation with a higher success rate and a shorter period of treatment than conventional protocols, and is the first one indicating the effectiveness on NS. The success rates varied according to diagnosis and location of skin lesions. High success rates were obtained for SL and PIH and on the face. The present protocol can be applied to almost any kind of skin lesions with hyperpigmentation, preferably when the intensity of pigmentation is very high.

Acknowledgement
   The authors express sincere appreciation to Yuka Kuwahara and Takako Kato for their assistance in spectrophotometric measurements.

Correspondence to: Kotaro Yoshimura, M. D.
Department of Plastic, Reconstructive, and Aesthetic Surgery, University of Tokyo,
7-3-1, Hongo, Bunkyo-Ku, Tokyo 113-8655, Japan.
Phone: +81-3-5800-8948
Fax: +81-3-5800-6929
E-mail: yoshimura-pla@h.u-tokyo.ac.jp
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 Legends
Fig. 1. Case 1: 54-year-old woman with a senile lentigine on the left cheek. (A) before treatment, (B) at 1 week, (C) at 2 weeks, (D) at 4 weeks, and (E) at 8 weeks. (F): Sequential changes in RMV, RHV. RMV: relative melanin value, RHV: relative hemoglobin value.

Fig. 2. Case 2. 60-year-old man with senile lentigines on the bilateral forearms. (A), (B): before treatment, (C), (D): at 2 weeks, and (E), (F) at 20 weeks.

Fig. 3. Case 3. 28-year-old man with postinflammatory hyperpigmentation of donor site of split-thickness skin graft on the medial aspect of the right upper arm. (A) before treatment, and (B) at 20 weeks.

Fig. 4. Case 4. 16-year-old woman with congenital nevus spilus on the left cheek. (A) before treatment, (B) at 3 weeks, (C) at 8 weeks, and (D) at 12 months.

Fig. 5. Case 5. 61-year-old woman with nevus spilus on the left cheek. (A) before treatment, (B) at 8 weeks, and (C) at 15 months.