Idiopathic Eruptive Macular Pigmentation: A Rare and an Under-reportedEntitySonam Sharma*

Department of Pathology, Kalpana Chawla Government Medical College, Karnal, Haryana, India*Corresponding author: Sonam Sharma, Department of Pathology, Kalpana Chawla Government Medical College, Karnal, Haryana, India, Tel: 09999841393; E-mail:drsonamsharma@gmail.com

Received date: April 21, 2018; Accepted date: June 25, 2018; Published date: August 2, 2018

Copyright: © 2018 Sharma S. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use,distribution, and reproduction in any medium, provided the original author and source are credited.

Abstract

Idiopathic eruptive macular pigmentation is an unfamiliar dermatological disorder which is characterized by thepresence of multiple discrete asymptomatic brownish-black macules and flat plaques involving the face, neck, trunk,and proximal extremities especially in pediatric population. It is important to differentiate this uncommon entity fromother pigmented dermatosis as it undergoes spontaneous resolution without any residual pigmentation or scarringand thus contraindicating any unnecessary aggressive therapeutic interventions. An experience of one such case ina 6-year-old Indian boy is being reported herewith so as to create awareness amongst the dealing physicians.

Keywords: Acanthosis nigricans; Children; Idiopathic eruptivemacular pigmentation; Pigmented papillomatosis; Urticariapigmentosa

IntroductionIdiopathic eruptive macular pigmentation (IEMP) is a rare, benign,

self-limiting and an under-diagnosed pigmentary skin disorder of anunknown etiopathogenesis [1]. This term was first coined in French byDegos et al. in the year 1978 [2]. This entity was first described inEnglish literature by Sanz de Galdeano et al. in 1996 who published 5cases of IEMP and based on the history, clinical presentation andhistological findings of these cases, they also established its diagnosticcriteria which comprised of following identifying characteristics: [a]eruption of brownish, nonconfluent, asymptomatic macules involvingthe trunk, neck, and proximal extremities in children and adolescents,[b] absence of preceding inflammatory lesions, [c] no previous drugexposure, [d] basal cell layer hyperpigmentation of the epidermis andprominent dermal melanophages without visible basal layer damage orlichenoid inflammatory infiltrate, and [e] normal mast cell count [3].This criteria for IEMP diagnosis has been widely accepted andsubsequently quoted in the published writings since then. However,recently an attempt has been made to revise the diagnostic criteria asauthors have speculated that IEMP can be considered as an eruptivevariant of acanthosis nigricans because of its close clinical andhistological resemblance to acanthosis nigricans i.e. velvety lesions onatypical sites and histological findings of pigmented papillomatosis [4].Paucity of the knowledge about this unfamiliar melanosis and debatesover its controversial existence as a separate disease entity promptedme to report a rare case of IEMP in a 6-year-old Indian boy who wasclinically misdiagnosed as a case of urticaria pigmentosa.

Case ReportA 6-year-old healthy boy presented with multiple brownish-black

lesions over the face, neck, trunk and bilateral proximal extremitiessince last 9 months. The lesions gradually increased in number and sizeover a period of 2 months and became stable since last month. There

was no history of any preceding skin lesion, associated pruritis andphotoaggravation of the lesions. History of any oral medications/supplements or any topical medicaments prior to the onset of theeruption was non-contributory. On detailed history taking, parents ofchild revealed that he was being treated for urticaria pigmentosaearlier but there was no improvement. The child was born of a non-consanguineous marriage. His birth, developmental, personal andfamily history was insignificant. The general physical and systemicexamination revealed no abnormality. His dermatological examinationexhibited multiple (approximately 40-50 in number), discrete, smooth,non-scaly, non-atrophic, normesthetic, round to oval hyperpigmented(brownish-black to gray) macules ranging from 0.5 cm to 3 cm indiameter over the face, neck, trunk, and both the upper extremitiesincluding flexural folds (Figure 1).

Figure 1: Numerous hyperpigmented macules on the forehead,cheeks, chin, neck, chest, abdomen, bilateral arms and the back.

Few of the lesions had a peculiar velvety surface. Mucosae, hair,nails, palms, and the lower extremities were spared. Darier’s sign wasnegative. The routine haematological, biochemical and microbiologicalinvestigations revealed no abnormality. Skin biopsy from one of thepigmented back lesion showed orthokeratosis, mild irregularacanthosis, slight papillomatosis and basal cell layerhyperpigmentation. The upper dermis showed sparse superficialperivascular lymphohistiocytic infiltrate with numerous melanophages

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DOI: 10.4172/2155-9554.1000459

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in the papillary dermis. The mast cell number was normal (Figure 2).Based on these clinical manifestations and histopathological findings, afinal diagnosis of IEMP was made. The patient was started on topicaltretinoin 0.05% application once daily. On 6 months follow-up thepreexisting lesions remained unchanged however, no worsening ordevelopment of new lesions was seen.

Figure 2: Histopathology of the lesional skin (A) Epidermisexhibiting orthokeratosis, mild irregular acanthosis, slightpapillomatosis, prominent melanin in the basal cell layer with theupper dermis showing melanophages and sparse superficialperivascular lymphohistiocytic infiltrate (Hematoxylin and eosin,40X) (B) Magnified view (Hematoxylin and eosin, 200X).

DiscussionIEMP is a rare under-reported skin disorder which is now regarded

as the clinical reminiscent of acanthosis nigricans lesions [5-7]. Aftercareful review of the pertinent literature till date, less than 50 cases ofIEMP have been documented worldwide with handful of them beingreported from India [1,5,6,8-12]. The largest series of 10 cases has beenpublished by Jang KA et al. from Korea [13]. The age of onset of thedisease ranges from 1 to 31 years with no sex predilection [14]. Theyoungest and oldest case described in the literature is that of a 1-year-old and 50-year-old [13,15]. The exact pathogenesis of this disease stillremains unclear. Researchers have postulated that hormonal factorsand autoimmunity are involved in increased pigment production inIEMP cases [13,14], whereas sunlight which plays a pivotal role inmany cutaneous disorders is not at all an important factor for it tooccur, as most of these lesions occur in photoprotected areas [16].Pang YZ et al. have observed that since majority of the IEMP casesreported in the literature involved the young patients of Indian descent(like in the present case), a genetic basis of this disease cannot be ruledout and requires further exploration [17].

Clinically, the characteristic eruption of IEMP is composed of roundto oval, circumscribed, non-pruritic, homogeneous pigmented maculesand plaques that appear without previous erythematous, papular, orhypochromic lesions, occurring mostly on the trunk, neck, andproximal portion of the extremities. However, lesions occurring in aChristmas tree pattern and limited to flexural areas of the body havealso been documented in the literature [18,19]. IEMP needs to bedifferentiated clinically and histologically from friction melanosis,post-inflammatory hyperpigmentation, fixed drug eruption (FDE),

urticaria pigmentosa, lichen planus pigmentosus (LPP), erythemadyschromicum perstans (EDP), pigmentary disorders that involve theflexural areas like Dowling-Degos disease and acanthosis nigricans asthese conditions can cause diagnostic conundrum and unnecessarytherapeutic interventions [13,19].

Friction melanosis occurs after prolonged rubbing of the skin withnylon towels/brushes and is characterized by skin hyperpigmentationover the bony regions of the back and limbs clinically and pigmentaryincontinence with sporadic deposition of amyloid in the papillarydermis on histopathology [20]. Post-inflammatory pigmentation isexcluded by the lack of clinical manifestations of a previous dermatosisthat commonly affects the dermal-epidermal interface, such as lichenplanus, benign lichenoid keratosis, and erythema multiforme [13]. InFDE, there is history of drug intake prior to the onset of eruption.Darier’s sign positivity and increase in the number of mast cellshistologically is seen in urticaria pigmentosa. LPP and EDP areconsidered to be the clinical variants of the same disease, as theirhistological findings are similar [21-23].

LPP is an uncommon variant of lichen planus which ischaracterized by hyperpigmented, dark brown macules in sun-exposedareas and flexural folds [24] whereas in EDP, slate gray macules withrim of erythema without any predilection for photoexposed sites areseen. Histologically, an atrophic epidermis, vacuolar alteration of thebasal cell layer with a scarce lymphohistiocytic lichenoid infiltrate andpigment incontinence are seen in LPP while in EDP, vacuolar changesof the basal layer and prominent pigmentary incontinence are evidenton histopathology. Ultrastructural studies in IEMP shows numerousmature melanosomes in basal and suprabasal keratinocytes andmacrophages containing clustered melanosomes, but no vacuolarpattern of the basal cell layer, discontinuity of the basal lamina, colloidbodies, or a lichenoid infiltrate that might indicate a diagnosis of LPPor EDP [3,23]. Dowling-Degos disease has an autosomal dominantmode of inheritance and shows a reticulate or confluent distribution.Pigmented comedone-like lesions, follicular hyperkeratotic papulesand perioral pitted acneiform scars are also its clinical features. Thinfiliform, pigmented interconnecting epithelial strands are itscharacteristic histopathological findings [25]. In acanthosis nigricanscharacteristic clinical features are brown velvety or verrucous plaquesand on histopathology, papillomatosis, hyperkeratosis and slightacanthosis without any basal cell layer pigmentation is seen [26].Histopathological findings of IEMP are acanthosis, basal layerhyperpigmentation, and dermal melanophages. There is no evidence oflichenoid infiltrate or basal cell layer damage and mast cells are normalin number. The other important characteristic histopathologicalfinding “pigmented papillomatosis,” has been mentioned by manyauthors hence, laying emphasis that it should be included as one of thediagnostic criteria for IEMP [4,12]. The present case fulfilled thediagnostic criteria of IEMP [3] i.e. both clinically andhistopathologically. However, there were certain lesions which werevelvety clinically and there was slight papillomatosis with presence ofbasal layer hyperpigmentation. However, there was no metabolicderangement in the present case. These findings further support thefact that IEMP can be considered as an eruptive variant of acanthosisnigricans without associated metabolic changes as documented in theliterature [5,6].

IEMP has a benign course and is a self-resolving condition. It hasbeen reported to disappear spontaneously within months to years [13].However, two unusual cases have been documented in the literature i.e.of a 24-year-old woman lasting 21 years who was characterized by

Citation: Sharma S (2018) Idiopathic Eruptive Macular Pigmentation: A Rare and an Under-reported Entity. J Clin Exp Dermatol Res 9: 459. doi:10.4172/2155-9554.1000459

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several periods of spontaneous resolution followed by recurrences [27]while the other case is of a 24-year-old man who presented with IEMPlesions of 20 years duration. The patient never had spontaneousresolution but his disease stopped progressing followed by a suddenaggravation 16 years later [12].

ConclusionIEMP is a rare dermatological condition which should always be

considered among differentials of the skin pigmentary disordersespecially in pediatric age group patients as it a separate entity withcharacteristic clinical and histological features. Medical unfamiliarityand reluctance of children to undergo skin biopsy has added to itsrarity and under-reporting. Nevertheless, a high index of suspicion andknowledge about this entity is important so as to avoid unnecessarytreatment because this condition spontaneously resolves with time.However, more insight is required to understand its genesis and torevise its diagnostic criteria in near future.

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Citation: Sharma S (2018) Idiopathic Eruptive Macular Pigmentation: A Rare and an Under-reported Entity. J Clin Exp Dermatol Res 9: 459. doi:10.4172/2155-9554.1000459

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J Clin Exp Dermatol Res, an open access journalISSN:2155-9554

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