Answer

Diagnosis: Annular atrophic lichen planus.

Review

Annular atrophic lichen planus (AALP) is a rare variant of lichen planus with only 9 case reports in the world literature. ^{[1],[2],[3],[4],[5],[6],[7]} Friedman and Hashimoto first described it 18 years ago in a black, middle-aged male with polygonal, violaceous papules present in an annular or arciform pattern over extremities and hips for 25 years. Topical steroids and UV light were of no help. ^[1] An old woman with a 20-year history of this condition did not respond to steroid creams. ^[2] The third was a middle-aged male with skin lesions for more than 20 years in association with Sneddon's syndrome. ^[3] Morales-Callaghan reported a case with duration of lesion for 3 years with no response to topical steroids. ^[4] The latest report is of 2 cases from China, of which one responded to topical steroids, while the other one did not. ^[7]

AALP is characterized by multiple, small, violaceous papules, which slowly expand peripherally with raised border and an atrophic center, with distribution similar to common lichen planus. Histopathology shows findings of lichen planus at the periphery, while central part shows a thinned out epidermis with flattened rete ridges. The elastic fibers in the papillary dermis are reduced or absent and appear fragmented on electron microscopy. ^[1] The diagnosis here was suggested by the chronic history of itchy skin lesion, the classical morphology of violaceous annular skin lesions, failure of response to topical steroids, and histopathology. From the central part, it revealed a thinned out epidermis with flattened rete ridges, degeneration of basal cell layer, and scanty upper dermal chronic inflammatory infiltrate [Figure 2], while near the edge, there was mild hyperkeratosis, hypergranulosis, irregular acanthosis, basal cell layer degeneration with saw-tooth rete ridges, an upper dermal, band-like chronic inflammatory infiltrate with melanin incontinence [Figure 3]a and b. The elastic fibers in the papillary dermis were reduced on special stain. Failure of response to 1% hydrocortisone acetate cream used previously and a good response to topical 0.1% tacrolimus ointment in 4 months also supported the diagnosis as reported earlier. ^{[1],[2],[3],[4],[5]}

The peculiar morphology of the lesions could be due to elastolytic activity of the inflammatory cells, resulting in the formation of loci of localized cutis laxa. ^[6],[8] Steroid-induced atrophy can be differentiated by observing a decrease and thinning of collagen bundles and pronounced appearance of the elastic fibers.

It is important to create awareness about this chronic, rare variety of lichen planus with usually poor response to topical steroids. Also, it is proposed that this condition be labeled as "chronic annular atrophic lichen planus (CAALP)," so as to delineate it as a distinct entity, having a chronic course as compared to the classical lichen planus.