Comparison of efficacy and safety of tretinoin 0.05% and glycolic acid peeling 70% in axillary and neck lesions of acanthosis nigricans: A single‐blinded, randomized trial

Acanthosis nigricans is a non‐inflammatory skin pigmentary disorder characterized by a dark, velvety appearance, primarily observed in the neck and axillary areas. It is commonly associated with obesity, diabetes, and insulin resistance. Although the primary treatment is correcting the underlying disorders, many aesthetic modalities have been established to improve appearance owing to cosmetic concerns.


| INTRODUC TI ON
[3] The attachment of insulin, insulin-like growth factor, and fibroblast growth factor 21 (FGF21) to receptors, such as fibroblast growth factor receptors (FGFR), tyrosine kinase receptors, and epidermal growth factor receptors (EGFR) leads to fibroblast and keratinocyte proliferation.The histopathologic features consist of mild acanthosis, hyperkeratosis, and papillomatosis. 1,4Hyperkeratosis is distinguished as the main element of dark skin rather than melanin accumulation. 4 is typically observed in obesity, diabetes, and insulin resistance.Although metabolic syndrome is considered the main cause of acanthosis nigricans, endocrinopathies, medications, malignancy, and genetic factors are also involved in disease etiology. 5,6Due to the increasing rates of diabetes and obesity and based on factors like age and ethnicity, the prevalence of AN ranges from 7% to 74%, with an equal incidence in males and females. 4,7,8e primary focus of therapy is to address and manage the root causes of the condition, which may include obesity, insulin resistance, medication-induced acanthosis drugs, and malignancy.In addition to these underlying conditions, the aesthetic disfigurements associated with the condition have prompted the development of various treatment options.These include topical treatments such as retinoids, chemical peels, and calcipotriol, as well as oral agents like oral retinoids and fish oil.[11][12] Ultimately, the drug of choice for AN has not yet been determined, and further trials are required to demonstrate the effectiveness of various modalities.In this single-blinded, randomized trial, we aimed to evaluate the effectiveness of tretinoin 0.05% which is considered the first-line treatment for AN, and to compare it with a 70% glycolic acid peeling solution.

| MATERIAL S AND ME THODS
This was a single (assessor)-blinded, randomized trial comparing the efficacy of glycolic acid 70% and tretinoin 0.05% in patients with axillary and neck AN lesions.This study was conducted between 2021 and 2022 and approved by the ethics committee.Informed written consent was obtained after patient enrollment, and all procedures were performed according to the ethical principles of the Declaration of Helsinki.
The inclusion criteria were (1) axillary or neck involvement, (2) no prior treatment for at least 1 month, (3) patients aged >12 years, and (4) patients who agreed to participate and understood the contents of the study.The exclusion criteria were as follows: (1) any contraindications for the use of topical tretinoin or glycolic acid, including contact allergy to topical agents; (2) pregnancy and lactation; (3)   malignancy; (4) withdrawal from the study for any reason; and (5)   unbearable and severe side effects of topical agents.
After enrolling the patients, demographic data, including age, sex, past medical history, drug history, and disease duration were recorded.After that, patients were carefully examined by a dermatologist and lesions were classified according to severity grading by Burke et al. 13 The classification consists of five locations (neck, axillae, knuckles, elbows and knees), and neck and axillae grading was used in our study on a scale of 0 to 4, as follows: Grade 0: Absent; no lesions were detectable on close distance.
Grade 1: The lesions were detected at a close distance, but the margins could not be measured.
Grade 2: Lesions were restricted to the base of the neck (<3 inches in width) or the center of the axillae.
Grade 3: The lesions were expanded from the base of the neck to the lateral sides (posterior border of the sternocleidomastoid, 3-6 inches), but were not visible from the front view or the whole axillary area was involved but lesions were not visible when the patient's arm was against the sides.Grade 4: Lesions were extended to the anterior sides of the neck (>6 inches) and were seen from the front view, or lesions of the axillae were visible from the front or rear when the patient's arms were against the sides.
After taking baseline photographs during the first session, the neck and axillary lesions were randomly divided into two treatment groups.The Randomized lesions were treated with cream tretinoin 0.05% every other night, and on the opposite side, glycolic acid 70% was applied at the clinic every 2 weeks for four consecutive sessions.
Response to treatment and possible side effects were evaluated every 2 weeks and patient satisfaction was recorded as follows: poor (0%-25%), moderate (26%-50%), good (51%-75%), and excellent (76%-100%).For any protocol changes, unbearable side effects, or patient dissatisfaction, the study could be terminated, and conventional treatments were substituted as needed.At the end of the eighth week, in addition to scoring by the main examiner and patient satisfaction, two blinded dermatologists evaluated the improvements based on the photographs taken during the first and 2 weeks after the last session.The improvements were qualitatively scaled as follows: poor (0%-25%), moderate (26%-50%), good (51%-75%), and excellent improvement (76%-100%).Adverse effects were recorded at each visit.

| Statistical analysis
Wilcoxon signed-rank test was used to compare the two treatment methods.An association linear-by-linear test was used to examine (1) the correlation between the severity of lesions and the percentage of the response to treatment, (2) the association between the severity of lesions and the percentage of the response to treatment, (3) the correlation between the severity of lesions and treatment satisfaction and (4) the association between the severity of lesions and treatment satisfaction.The data were analyzed using SPSS version 26, and the level of significance was set at p < 0.05.

| RE SULTS
A total of 30 patients participated in the study, ranging in age from 12 to 45 years old, with an average age of 25.27 ± 10.74.Among these patients, those with axillary lesions were aged between 12 and 41, with an average age of 24.88 ± 9.85, while those with neck lesions were aged between 12 and 45, with an average age of 25.71 ± 10.92.
The patients had a body mass index (BMI) ranging from 23 to 44, with an average BMI of 29.67 ± 4.92.In the group with neck lesions, the BMI ranged from 23 to 44, with an average BMI of 30.86 ± 5.46, while in the group with axillary lesions, the BMI ranged from 23 to 38, with an average BMI of 28.63 ± 4.30.There was no significant difference in BMI and age between patients with axillary and neck lesions (p > 0.05).
Out of the total participants, 70% had the disease for <7 years.
13.3% had it for 7-15 years, and 16.7% had it for 15-20 years.43.3% of the patients did not report any underlying disease or family history, while 6.6% had diabetes.Most patients (83.3%) had not received any prior treatment for their lesions.
Regarding the response to tretinoin treatment, in the neck lesion group, 57.1% had a poor response, 21.4% had a moderate response, and 7.1% had a good response, with only 14.3% showing an excellent response.In the axillary lesion group, 37.5% had a moderate response, 25% had a poor response, 18.8% had a good response, and 18.8% had an excellent response.
Eleven patients (78.6%) in the neck lesion group experienced a poor response to glycolic acid treatment.No excellent response was observed in any of the patients in this group.Moreover, eight patients (50%) with axillary lesions showed a poor response, and a single patient showed an excellent response to glycolic acid.
When it comes to patient satisfaction, in the neck lesion group, 42.9% had moderate satisfaction with tretinoin, and only one patient reported excellent satisfaction.Similarly, in the axillary lesion group, 37.5% had moderate satisfaction, while 31.3% reported excellent satisfaction.
No patient in the neck lesion group had excellent satisfaction with glycolic acid while 5 (35.7%) had poor satisfaction.In the axillary lesion group, only one patient expressed excellent satisfaction (6.3%) while six patients (37.5%) had poor satisfaction with glycolic acid treatment.
In the neck lesion group, comparing the two treatments based on the Wilcoxon test, no significant difference was observed between the percentages of responses to treatments by two blinded dermatologists.Tretinoin had significantly superior effects in the axillary lesion group than glycolic acid (p < 0.05%).Thus, tretinoin was more efficacious in the treatment of axillary lesions.There was no statistically significant difference in patient satisfaction between the two treatment methods in patients with neck lesions (p > 0.05).
In the axillary lesion group, there was a significant difference in patient satisfaction compared with tretinoin and glycolic acid (p < 0.05), showing that patients were more satisfied with tretinoin treatment.(Table 2).None of the patients in the glycolic acid treatment group experienced any side effects.The adverse effects of tretinoin are shown in Table 3.
Based on the linear-by-linear association test, the percentage of patient satisfaction and response to tretinoin treatment decreased with an increase in the severity of AN in the neck and axillary lesion groups.There was a clinically significant relationship between the increase in the severity of AN lesions and the percentage of response to tretinoin treatment, which showed the response to tretinoin decreased as the number of grades increased, However, the linear-by-linear association test did not show any statistical significance between the severity and percentage of patients' satisfaction and response to tretinoin treatment (p > 0.05).(Table 4).
While there was no statistically significant difference between the severity of lesions and the percentage of response to glycolic acid treatment in the neck lesion group (p > 0.05) in the axillary lesion group, as the number of grades increased, the percentage of response to glycolic acid treatment decreased.(p < 0.05).
In the neck lesion group, there was no statistically significant correlation between the severity of lesions and the percentage of patient satisfaction with glycolic acid (p > 0.05).In the axillary lesion group, a statistically significant negative correlation was observed between the number of grades and the percentage of satisfaction with glycolic acid treatment (p < 0.05).(Table 5).
Figures 1 and 2 show the neck and axillary lesions treated with tretinoin and Glycolic acid peeling.

| DISCUSS ION
AN is a cutaneous disorder that commonly presents as symmetrical plaques with velvety hyperpigmentation in the color spectrum from brown to black.[16] Glycolic acid (GA) is a chemical peeling that affects the very superficial to medium dermis, depending on the percentage.[19] Exfoliation is the final result of "cathepsin D" activation,  TA B L E 3 Side effects of tretinoin.

Side effects of tretinoin treatment Number
No side effects 10 (33.3%)Slight erythema 18 (60%) Slight erythema with scaling 2 (7.6%) In a comparative study by Fathy et al. 20 patients with pseudoacanthosis nigricans of the neck were treated with glycolic acid 70% compared to fractional CO2 laser.No significance was found comparing the modalities, nevertheless, glycolic acid was more effective in improving mean area, severity, and texture. 20r findings showed no statistically significant difference between the two methods when comparing glycolic acid and tretinoin efficacy in neck lesions.Furthermore, in terms of patient satisfaction, the two treatments were not significantly different.In contrast, tretinoin showed superior responsiveness and satisfaction in axillary lesions compared to glycolic acid (p = 0.02, p = 0.008, respectively).
This responsiveness may be attributed to the enclosed space in the axillary area after the use of tretinoin.This environment is similar to that of an occlusive dressing, which results in increased permeability and efficacy.Rajegowda et al. compared topical tretinoin (0.025%) with a chemical peel (trichloroacetic acid) for AN lesions.These findings showed that tretinoin was more efficacious in improving lesions.
Consistent with our study, this study also showed that tretinoin had a greater incidence of adverse effects than peels. 1 Although the main treatment for AN is to correct the underlying reasons, resolving the appearance flaws like hyperpigmentation will increase the patient's quality of life. 23Topical retinoids are considered the first-line treatment for this disease.This group of treatments regulates epidermal turnover, helps to adjust hyperkeratosis, and makes epidermal thickness return to normal condition. 4,16 date, few studies have considered the impact of chemical peels such as glycolic acid on acanthosis lesions, especially in the axillary area.Although retinoids are the first-line treatment option, according to past studies, chemical peels may play a crucial role in treating AN.The superiority of chemical peels is a topic that should be discussed in future research.

TA B L E 4
The correlation between the number of grades of the neck and axillary lesions and tretinoin treatment.

TA B L E 5
The correlation between the number of grades of the neck and axillary lesions and glycolic acid treatment.The strength of our study was that it evaluated improvements by blinded dermatologists, which is required to minimize the risk of bias.The other point was a within-subject comparison using both treatments in all individuals.This method eliminates individual differences and reduces confounding factors, including genetic factors.
Future research warrants larger sample size and multi-clinic practices to extend the results to the general population.

| CON CLUS ION
Our findings demonstrated that tretinoin was more effective than glycolic acid in treating axillary lesions, and patients were more satisfied with its results.Moreover, a negative correlation was found between the number of grades and response to both treatments in the neck and axillae.However, further trials with larger sample sizes and control groups are required to confirm the findings.

AUTH O R CO NTR I B UTI O N S
Maryam Ghiasi: conceptualization, methodology, study design and editing, Raana Samii: methodology, data collection, follow-up, drafting, editing and analysis, Nasim Tootoonchi and Kamran Balighi: supervision, Sama Heidari: drafting and editing.

2 TA B L E 2
which is activated and synthesized through acidification of the stratum corneum.The use of GA was first reported by Ichiyama et al.In this study, two Japanese patients with familial generalized AN were treated with gradually increasing percentages of glycolic acid.A 3-year follow-up demonstrated the treatment successfully had improved and maintained the skin condition.Comparing response to treatment and patient's satisfaction between two methods.

F I G U R E 1 A
patient with neck lesion, before initiating the treatment (A) and 8 weeks after the treatment with tretinoin (B), before treatment with Glycolic acid peeling (C) and 8 weeks after treatment (D).U R E 2 A patient with axillary lesions, before treatment (A) and 8 weeks after the treatment with tretinoin (B), the other side before treatment (C) and 8 weeks after treatment with Glycolic acid peeling (D).

TA B L E 1
Demographic characteristics of participants.

Glycolic acid Grade of the neck lesion p-value Grades of the axillary lesion
*L: association linear-by-linear.**Level of significance: p-value<0.05.