|Year : 2014 | Volume
| Issue : 2 | Page : 100-102
Linear lichen planus pigmentosus: A rare entity with an illusory presentation
Anupam Das1, Vivek Mishra1, Indrashis Podder1, Piyush Kumar2, Dipti Das1, Nilay Kanti Das1
1 Department of Dermatology, Medical College and Hospital, Kolkata, West Bengal, India
2 Department of Dermatology, Katihar Medical College, Katihar, Bihar, India
|Date of Web Publication||15-Dec-2014|
"Prerana", 19, Phoolbagan, Kolkata - 700 086, West Bengal
Source of Support: None, Conflict of Interest: None
We report a case of lichen planus pigmentosus (LPP) that developed in a linear pattern, that too over nonsun-exposed areas. The patient presented with linear dark brown macules and patches on the back in the midline. Skin biopsy showed features consistent with a diagnosis of LPP. LPP should be considered in the clinical differentials of linear hyperpigmented skin lesions.
Keywords: Lichen planus pigmentosus, linear, nonsun-exposed areas
|How to cite this article:|
Das A, Mishra V, Podder I, Kumar P, Das D, Das NK. Linear lichen planus pigmentosus: A rare entity with an illusory presentation. Pigment Int 2014;1:100-2
| Introduction|| |
Lichen planus pigmentosus (LPP) is a rare variant of lichen planus (LP). The presence of linear LPP in children is an infrequently encountered entity.  It, usually, manifests as mottled or reticulated hyperpigmented, dark brown macules in sun-exposed areas and flexural folds. The histopathologic findings of LPP consist of hyperkeratosis, atrophic epidermis with hydropic degeneration of the basal layer, and scanty dermal lymphohistiocyte or lichenoid infiltrates along with pigmentary incontinence and the presence of melanophages.  Although there are quite a number of reports of linear LP, LPP with a linear pattern is seldom encountered.
| Case Report|| |
A 7-year-old girl presented with itchy dark brown patches over the covered interscapular area in a linear fashion. It began as a small macule which gradually evolved to multiple patches in a linear arrangement over the last 6 months. There was no history of preceding erythema or scaling. There was no history of significant sun exposure. Family history was non contributory. No history of any preceding drug intake, contact with chemicals, perfumes or plants was present.
On examination, the patient had linear arrangement of dark brown patches over the midline of back, in nonsun-exposed interscapular area from above downward [Figure 1]. There were a few discrete patches over the scapulae as well. There were no similar skin lesions over other areas of the body, including the sun-exposed sites and intertriginous areas. Mucosa, scalp, and nails showed no associated changes. The clinical differentials considered in the case were postinflammatory hyperpigmentation, LPP, ashy dermatosis, and persistent Mongolian spots. Skin biopsy from a representative lesion showed basal layer degeneration, pigment incontinence, melanophages, patchy infiltrate, perivascular inflammation which are consistent with LPP [Figure 2]. The patient was advised direct immunoflourescence study of skin biopsy; however, it could not be done due to financial constraints. The patient was counseled regarding the nature of the disease and its prognosis. He was advised topical treatment with hydroquinone plus retinoid and tacrolimus ointments; however, he failed to show up for follow-up, persistent counseling.
|Figure 1: Linear arrangement of dark brown patches over the midline of the back|
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|Figure 2: Photomicrograph showing hypermelanization of the basal layer, pigment incontinence, and patchy infi ltrate (H and E, ×40)|
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| Discussion|| |
Lichen planus pigmentosus, an uncommon variant of LP, is a disease of third or fourth decade and is characterized by insidious onset of dark brown macules in sun-exposed areas and flexural folds with or without slight pruritus. The pathogenesis of LPP remains elusive, however, the role of CD8 + T-lymphocytes along with mediators such as interferon-g, tumor necrosis factor-α, interleukin 6, and lymphocyte function-associated antigen 1 has been found to be substantial. It may have diffuse, reticular, blotchy, linear or perifollicular distribution.  Pigmentation varies from slate grey to brownish-black although in a single patient it is generally uniform. Diffuse form is the commonest type of pigmentation.  The face and neck are the most frequent initial sites of involvement. Pock et al. observed a predominance of lesions occurring in intertriginous areas, mostly axillae, and thus proposed the nomenclature "LPP-inversus."  Other dubious presentations include zosteriform pattern on the trunk,  segmental distribution,  and involvement of nonsun-exposed areas like thigh.  The main histopathological features of LPP include atrophy of the epidermis, vacuolar degeneration of the basal cell layer and scarce dermal perivascular or lichenoid infiltrate. The presence of dermal melanophages and pigment incontinence are the two constant features seen in histopathology.  This pigmentary disorder is fairly persistent and responds poorly to treatment, thus producing substantial cosmetic disability. The etiology is unknown but various factors (e.g., viral infections and certain topical agents including mustard oil, amla oil, and henna hair dyes) can act as a trigger. Sunlight probably plays a role in inciting LPP. The disease has a long clinical course. There is a raging confusion whether LPP and ashy dermatosis (our main differential) are the same conditions. However, several authors consider them to be different conditions; based on some subtle differences. Some of the important differences between these two closely related disorders have been tabulated [Table 1]. The other differentials which deserve special mention are macular variety of discoid lupus erythematosus (DLE) (scarring, atrophy, erythema, dyspigmentation, typical holoprosencephaly [HPE] features showing absence of basal layer degeneration and melanin incontinence); other linear disorders like linear variety of fixed drug eruption (typical drug history esp. trimethoprim, temporal association with drug intake, distinctive HPE) and focal dermal elastolysis (yellowish skin nodules, skin HPE showing degeneration of elastic tissue). In our case, LPP was diagnosed on the ground of typical HPE and lack of specific history and clinical features of the above mentioned disorders (e.g., lack of scarring, atrophy, erythema ruling out macular DLE; lack of any drug history ruling out linear variety of fixed drug eruption).
Lichen planus pigmentosus is an uncommon variant of LP, for which no effective treatment is available. Multiple drugs have been used including topical steroids, topical tacrolimus, keratolytics,  hydroquinone with/without retinoic acid, azelaic acid, kojic acid, and glycolic acid with varying rates of success.  Vitamin A has also shown promise as a treatment modality for LPP.  Some cases respond to a 10% aqueous solution of dimethyl sulfoxide applied topically. Other drugs which have been used with inconsistent results are griseofulvin, prednisone, etretinate, and chloroquine. Recently, 1064 nm-Q-switched neodymium-doped yttrium aluminum garnet laser in combination with topical tacrolimus has shown some promise in the treatment of this frustrating disorder (1.8 J/cm 2 every 3 weeks for about 4 months).  However, more reports are needed to substantiate this mode of therapy. The paucity of reports of localized linear configuration of LPP in non-sun-exposed areas of a child prompted the present report.
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[Figure 1], [Figure 2]
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