Therapeutic Response of Trichloroacetic Acid Peel in Patients With Acanthosis Nigricans

INTRODUCTION

Acanthosis nigricans (AN) is clinically characterised by hyperpigmented velvety plaques and shows papillomatosis and hyperkeratosis on histopathology. AN is a difficult-to-treat dermatosis, despite the use of various treatment modalities. Trichloroacetic acid (TCA) is stable, inexpensive, and easily accessible, and has shown effectiveness in photoaging and AN previously as well; hence, we planned to evaluate its use in our study.

MATERIAL AND METHODS

This case series describes 10 adult patients with AN who presented to the outpatient Department of Dermatology and Venereology of a tertiary care hospital. Clinically diagnosed cases of AN over the neck, without any history of topical and systemic treatment for AN in the past 3 months, were included, and written informed consent was obtained. Patients with hypersensitivity to TCA, keloidal tendencies, pregnant or lactating females, active infections at the site of the peel, type 2 diabetes mellitus, or any chronic illness, and unrealistic expectations were excluded. Patients with AN were graded according to the standard neck severity scale of 0–4, assessed by trained dermatologists^[1] [Table 1]. Patients were assessed by a trained dermatologist every fortnight to evaluate the improvement and adverse effects for 2 months. The patients were evaluated using a grading system, i.e., Minimal (0%–25%), Moderate (26%–50%), Good (51%–75%), and Excellent (>75%) improvement.

PROCEDURE

Priming was performed with sunscreen 2 weeks prior to the first session of the TCA peel. After the post-auricular test peel was performed to check for hypersensitivity in each patient, 15% TCA was applied using a brush in a single pass. Feathering was done at the edges to avoid demarcation lines. Later on, the area was cleaned with cold water. Patients were advised strict sun-protective behaviour. Diffuse erythema and cloudy frosting were considered the end point of the session, which clears within 10–15 minutes. The procedure was done every fortnight for a total of four consecutive sessions. Only regular sunscreen was advised in the morning after a bath. Weight reduction or any lifestyle measures were not advised during treatment.

RESULTS

Out of 10 patients, eight were females and two were males. All patients were of Fitzpatrick skin type 4–5 with a mean age of 33.5 years and a mean body mass index of 24.45 kg/m². One patient did not visit after two sessions of peeling, although no side effect was seen during treatment. Grade 4, grade 3, and grade 2 AN over the neck were seen in four, three, and three patients, respectively. Three patients showed minimal improvement, four patients showed moderate improvement, and two patients showed good improvement in AN lesions [Figures 1–3]. Side effects, including a mild, immediate burning sensation, were observed in all nine patients. Three patients also exhibited mild skin desquamation, which improved within a few days [Table 2].

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Figure 1:

(a) 31-year-old female patient with grade 4 AN (baseline). (b) Good response (51%–75%) after four sessions of TCA peel. AN: Acanthosis nigricans, TCA: Trichloroacetic acid.

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Figure 2:

(a) Second patient of grade 3 AN (baseline). (b) Moderate response (26%–50%) after four sessions of TCA peel. AN: Acanthosis nigricans, TCA: Trichloroacetic acid.

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Figure 3:

(a) 26-year-old male patient with grade 3 AN (baseline). (b) Moderate response (26%–50%) after four sessions of TCA peel. AN: Acanthosis nigricans, TCA: Trichloroacetic acid.

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DISCUSSION

The term “AN” was introduced by Unna, and the first case was described by Pollitzer in 1890. AN is characterised by velvety, hyperpigmented plaques, which affect major flexures, such as the neck, axillae, groins, antecubital, and umbilical areas. Initially, it starts as hyperpigmentation, followed by increased skin markings without induration. Curth has classified AN as four types, including pseudo, benign, malignant, and syndromic.

The exact etiopathogenesis is unknown; various factors have been proposed, including insulin resistance being the most important. Insulin at higher concentrations activates the IGF-1 (insulin-like growth factor 1) receptor and mediates epidermal cell proliferation.^[2] Elevated levels of growth factors, such as transforming growth factor α (TGF α) and epidermal growth factor (EGF), stimulate fibroblasts and keratinocytes, leading to cell proliferation. Various drugs have also been associated with AN. Histopathology of AN shows papillomatosis and hyperkeratosis of the skin. Epidermal hyperkeratosis is the primary cause of pigmentation in AN with minimal increase in melanin.

TCA (15%) causes damage to the epidermis, which is subsequently repaired, thus acting as a superficial exfoliative agent. It is a caustic agent that causes the precipitation of protein, leading to necrosis, which activates the wound repair mechanism, followed by re-epithelialization, resulting in an improvement in skin texture.^[3] TCA is a stable product; hence, absorption and depth of action correlate with the intensity of frost. TCA (≥15%) reaches the upper reticular dermis and causes collagen necrosis, associated with severe adverse effects.^[4]

Management of AN includes identification of the underlying cause, if any. Commonly used topical agents for the management of AN are tretinoin, salicylic acid, alpha-hydroxy acids, urea, and calcipotriol. Tretinoin is the most commonly used topical treatment for AN. Oral isotretinoin has also been used in extensive cases of AN. Lasers, including fractional CO₂, fractional 1550-nm Er-YAG, and long-pulsed Alexandrite lasers, have also been used in AN.^[5]In our study, TCA peel (15%) provided moderate to good results in terms of efficacy and safety, which is comparable to studies available in the literature.^[3,6] Rajegowda et al.^[3] conducted a randomised controlled study comparing the safety and efficacy of TCA peel versus topical tretinoin with n = 41, showing moderate improvement (26%–50%) in 10 and 17 patients, respectively, after 2 months. They concluded that topical tretinoin is more efficacious than TCA peel, and it can be considered as a first-line agent for the management of AN. Another randomised open-label study conducted by Bharati et al.^[6] comparing the efficacy of TCA (15%) peel versus glycolic acid (35%) peel in AN with n = 40, concluded that TCA peel has better efficacy as compared with glycolic acid peel after three sessions done at 2-week intervals.

CONCLUSION

15% TCA peel can be considered a treatment option for AN because it is safe, effective, and well-tolerated, with good patient compliance.