Nevoid acanthosis nigricans: Report of four cases localized to the umbilicus

Introduction

Acanthosis nigricans is a mucocutaneous disorder of keratinization that presents as hyperpigmented plaques with a keratotic surface and velvety appearance. Generally, it is distributed symmetrically in the folds of the neck, axillae, and/or groins and is considered a common dermatological manifestation of systemic illnesses or a reaction to certain medications.^1,2 On the other hand, nevoid acanthosis nigricans is a rare and benign form of acanthosis nigricans with only 24 cases documented in indexed literature.^3-21 Of these, only 2 are localized exclusively to the umbilicus.^6,8

Case Reports

Four patients attended the Dermatology Institute of Jalisco, “Dr. José Barba Rubio.” Three of them were females, with a median age of 19 years. The condition was present a while before presentation, with a median evolution time of 2.5 years [Table 1]. All the patients presented with the characteristic features of well- defined hyperpigmented-brownish plaques with verrucous, scaly surface, localized to the umbilicus [Figures 1a, 1b, 1c, 1d (×40)]. In all cases, the lesions were vigorously rubbed with alcohol swab, to test if they could be removed by doing so, and none could be removed. Thereafter, skin biopsies were performed. The histopathology studies in all the four cases showed similar features characterized by the presence of hyperkeratosis, mild and irregular acanthosis and papillomatosis [Figures 2a, 2b, 2c, 2d]. None had any associated symptoms or had received previous treatments. There was no family history of similar dermatosis or other disturbances of keratinization. They were not overweight or obese, and did not have similar lesions elsewhere. A diagnosis of nevoid acanthosis nigricans was established through clinical and histopathological data. Two patients, whose fasting insulin and glucose levels were within normal limits, received treatment with calcipotriol cream (50 μg/g) two times per day for 3 weeks, with remission of the lesions and without relapse at 3 years of follow-up. The other two patients did not agree to having diagnostic tests performed and declined treatment when they were informed about the benign nature of their condition. Figures 3a and 3b illustrates the improvement observed in patient number 2.

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Figure 1a:

Patient 1 showing a well defined hyperpigmented brownish plaque with verrucous, scaly surface

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Figure 1b:

Patient 2 showing a well defined brownish plaque with hyperkeratosis areas and exophytic appearance

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Figure 1c:

Patient 3 showing a verrucous brownish plaque with scaly surface and precise borders

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Figure 1d:

Patient 4 showing a verrucous brownish plaque with velvety appearance and precise borders

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Figure 2a:

Histopathology of patient 1 showing hyperkeratosis and papillomatosis (H and E, ×400)

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Figure 2b:

Histopathology of patient 2 showing hyperkeratosis, mild and irregular acanthosis with papillomatosis (H and E, ×400)

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Figure 2c:

Histopathology of patient 3 showing hyperkeratosis and papillomatosis alternating with moderate acanthosis, interpapillary valley filled with keratine (H and E, ×400)

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Figure 2d:

Histopathology of patient 4 showing hyperkeratosis and mild papillomatosis of the epidermis with scarce lymphocytic infiltrate on the dermis (H and E, ×400)

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Figure 3a:

Brownish hyperkeratotic and exophytic plaque localized to the umbilicus of patient 2 (×40)

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Figure 3b:

Clinical image showing clearance of the lesion after three weeks of treatment with topical calcipotriol (×40)

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Discussion

Nevoid acanthosis nigricans is a rare and benign form of acanthosis nigricans that can present during infancy or puberty.^3-21 It was first described in 1976 by Curth.³ Since that description, there have been 23 cases published.^4-21

Nevoid acanthosis nigricans presents slightly more often in males, is localized to bodily areas that differ from the classic acanthosis nigricans, is generally unilateral, and is distributed in segmental form or follow Blaschko’s lines. In published cases, the most frequent localization reported is in the trunk, in 79% cases, followed by extremities in 13%, and the head in 8% cases.^3-21 Only two (8%) of the reported cases are localized exclusively to the umbilicus^6,8 [Table 2].

From the morphological point of view, though it presents as a hyperpigmented and well-defined velvety-surfaced plaque, its distribution is nevoid.⁸ The other names that it has been given are -rounded and velvety epidermal nevus,^7,18,19 linear acanthosis nigricans,¹⁶ unilateral nevoid acanthosis nigricans,^{4,11,14,17,20,21} or acanthosis nigricans similar to epidermal nevus.^3,12

Its clinical course is unpredictable as it can have a short period of activity, to later maintain stability, or it can regress.^3,5 Contrary to classical acanthosis nigricans,^1,2 nevoid acanthosis nigricans is not associated with insulin resistance, diabetes mellitus type 2, obesity; internal malignant neoplasia, or endocrine diseases.^4-10,13-21 In 2006, Ersoy-Evans et al. published four cases of nevoid acanthosis nigricans where one was associated with obesity and amenorrhea, but since the patient also had classical and bilateral acanthosis nigricans lesions; we consider that the said associations were not related to nevoid acanthosis nigricans but rather to the classical acanthosis nigricans.¹² Other associations include epidermal nevus,³ neurofibromatosis,¹¹ and Hashimoto thyroiditis,¹² although a causal relationship has not been demonstrated between them, and the majority of the published casesdo not refer to any association with systemic illnesses.^4-10,13-21

The histopathological features of nevoid acanthosis nigricans do not vary from the classical form; characterized by hyperkeratosis, papillomatosis, mild and irregular acanthosis in the epidermis, with mild perivascular mononuclear inflammatory infiltrate in the superior dermis.^3-21 In some cases, hyperpigmentation of the basal layer has been reported.^{10,13-15,17-19}

The differential diagnoses that have been mentioned in published cases include the epidermal nevus,^{5,6,11,12,16-20} confluent and reticulated papillomatosis,^6,12,17 Dowling– Degos disease,⁶ and seborrheic keratosis.^17,18 To this list, we would add dermatosis neglecta and psoriasis [Table 3].^22-26

Clinically, psoriasis could be ruled out on the basis of the following features: 1) patients do not present with lesions in other areas and 2) the lesions are not erythematous plaques with desquamation on the surface. It is well-known that the umbilicus is a habitual localization for psoriasis, but, being a cutaneous fold, the lesions tend to be more erythematous and less desquamative, or in fact do not present scales.²⁷ In a Medline search using the key words “psoriasis,” “localised,” “nevoid,” and “special localisation,” we did not find descriptions of psoriasis with exclusive localization to the umbilicus.

Histological features, especially the lack of granular layer and regular papillomatosis could point toward psoriasis. However, these findings are non-specific and can also be present in nevoid acanthosis nigricans and other pathologies such as confluent and reticulated papillomatosis of Gougerot and Carteaud.²³ Moreover, our cases lack findings that are observed in 90% of patients with psoriasis (parakeratosis, dermal perivascular lymphocytic inflammatory infiltrate) or in more than 50% of them (Kogoj’s spongiform pustules and Munro micro abscesses).²⁸

Due to the rarity of nevoid acanthosis nigricans, there is no existing consensus for treatment and the results have been variable [Table 2]. We decided to initiate treatment with vitamin D analogs, specifically topical calcipotriol (22-ene-26,27-dehydro1α,25(OH) 2D3), for two reasons: a) for its mechanism of action on keratinocytes:in vitro studies have demonstrated that once vitamin D analogs bind to the intracellular receptor of vitamin D, they act as transcription factors modulating the expression of various genes involved in epidermal proliferation, inflammation, and keratinization.²⁹ In other words, calcipotriol promotes the differentiation of keratinocytes through molecules such as involucrin and transglutaminase-1 and inhibits epidermal proliferation,³⁰ b) For the favorable response observed in patients with nevoid hyperkeratosis of the nipple and areola when treated with calcipotriol³¹ or with another vitamin D analog, the calcitriol.³² These are the characteristics of the medication explaining the favorable response to treatment in two of the cases mentioned in the present case report, although this response needs to be confirmed in a greater number of cases.

We report these four patients with nevoid acanthosis nigricans localized to the umbilicus with the aim of familiarizing dermatologists with the clinical characteristics of nevoid acanthosis nigricans, help differentiate it from classical acanthosis nigricans and from other clinical and histopathological differential diagnoses and to consider it among the dermatoses localized to the umbilicus.