Lichen Planus Pigmentosus with Atypical Presentation-A Case Report

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Introduction
L ichen planus pigmentosus (LPP) was first described by Bhutani et al. 1 The lesions are small, brown to black, oval macules which can progress to form diffuse pigmented areas.The pigmentation may be diffuse, reticulate, blotchy, or perifollicular, usually symmetrical in distribution but may be found in a segmental, zosteriform, or blaschkoid pattern. 2 Here we report a diffuse Lichen planus pigmentosus presenting over photo-protected sites sparing sunexposed and flexural folds.

Case Report
A 21-year-old male, server at a restaurant, hailing from Assam, presented to the dermatology OPD with complaints of asymptomatic black discoloration mainly over the back, neck, arms, and thighs for 4 months.Patient first noticed a brown to black asymptomatic lesion over the upper left scapular region, which gradually spread to involve the entire back, abdomen, bilateral shoulders, lateral aspect of the upper arm, buttocks, thighs, and lower legs.There was no history of preceding erythema or erythematous borders over the lesions, which is generally seen in Erythema Dyschronicum Perstans.There was a history of occasional application of

Discussion
Lichen planus pigmentosus (LPP) is a chronic inflammatory pigmentary disorder essentially seen in adults after the age of 30.It occurs in both sexes but shows a female preponderance.It has been reported to occur predominantly in people with darker skin. 1 Several agents have been reported to act as predisposing factors.The occurrence in exposed areas in many patients has led to the proposition that sunlight may be a principal etiological agent.][9][10][11] Another variant is LPP-inversus, described in 2001 by Pock et al., defining it as a variant of LPP limited to intertriginous and flexural regions, sparing sun-exposed areas. 12,13ermoscopic findings show discrete brownish to bluish-grey dots, globules, blotches, rods and white lines against a diffuse brownish background.Brown indicates epidermal pigmentation, while the grey and blue dots indicate melanin incontinence in the papillary and reticular dermis. 14,15he histologic findings of LPP show hyperkeratosis and atrophy of the epidermis with vacuolar degeneration of the basal layer.A perivascular lymphohistiocytic infiltration and pigmentary incontinence in the dermis are also noted. 3,7,9he most common differential diagnosis of LPP include idiopathic eruptive macular pigmentation, erythema dyschromicum perstans, Riehl's melanosis, ochronosis, hori nevus, fixed drug reaction, and post inflammatory hyperpigmentation. 16,17

Differential diagnosis Comment Idiopathic eruptive macular pigmentation
Occurs in younger patients.Brown to grey macules start in the middle area of the trunk and then spread to proximal areas of the limbs.Histopathology reveals pigmentation of the basal layer with mild perivascular inflammatory infiltrate.It is an epidermal hypermelanosis and does not show significant melanophages in the papillary dermis. 16,17,18hy dermatosis/erythema dyschromicum perstans EDP presents with blue-grey, regularly shaped, hyperpigmented macules compared with dark brown, irregularly shaped, and illdefined hyperpigmented macules in LPP with erythematous raised active borders.Histopathological evaluation reveals superficial dermal melanin and melanophages in LPP, whereas EDP usually has deep dermal melanophages, giving rise to the characteristic browngrey color in LPP and the bluish-grey hue in EDP. 16,19,20 hl's melanosis/pigmented contact dermatitis It is characterized by facial hyperpigmentation, most pronounced on the forehead and in the zygomatic and/or temporal region.A correlation with clinical history of contactants and positive patch testing is necessary. 16,17hronosis History of hydroquinone use at high concentration for a prolonged period, most commonly on the face.Usually does not affect neck and flexural areas. 16ri nevus Bluish-grey or dark brown 2-5 mm macules caused by dermal melanocytes affecting the cheeks, temples, or forehead.Biopsy confirms diagnosis. 16xed drug reaction Round, initially erythematous macules with history of medication intake prior to onset. 16st inflammatory pigmentation Previous history of dermatosis which leaves pigmentation as it subsides. 16

Conclusion
This case exhibits LPP over atypical sites, including a wide region of grey-brown patches occurring on the photo-protected sites sparing the sun-exposed and intertriginous areas showing characteristic histologic features of Lichen planus pigmentosus.

Figure 1
Figure 1 (a, b, c): Absence of lesions over face, neck, and hands Figure 1 (d, e, f): Diffuse hyperpigmentation over arms, abdomen, and back