45 | CLINICAL, DERMOSCOPIC AND HISTOPATHOLOGICAL FEATURES OF A RARE CASE OF ERUPTIVE ANNULAR LICHEN PLANUS

V. Filastro¹, M. Ferrante^2|3, L. Gini^2|3, G. Martelli^2|3, M. La Placa^2|3, I. Neri³ | ¹Dermatology Unit, Health Science Department, Magna Graecia University, Catanzaro, Italy; ²Department of Medical and Surgical Sciences, Alma Mater Studiorum, University of Bologna, Italy; ³Dermatology Unit, IRCCS Azienda Ospedaliero-Universitaria di Bologna, Policlinico S. Orsola-Malpighi, Bologna, Italy

Introduction. Annular lichen planus (ALP) is an uncommon variant of lichen planus characterized by annular brown-violet plaques with an atrophic or lighter central area. Lesions may be solitary or multiple and typically affect intertriginous regions and male genitalia (glans); less frequently extremities, trunk and neck are involved. ALP is already uncommon, and the eruptive variant is even rarer, with only a few cases described in the literature. Here we report such an eruptive form of ALP observed in the Dermatology Unit of IRCCS Policlinico Sant’Orsola–Malpighi (Bologna).
Materials and Methods. Dermatological clinical examination, manual and digital dermoscopy were performed. A biopsy of one lesion was obtained and histopathological study was carried out.
Results. The patient, a 49-year-old man (Fitzpatrick IV) from Pakistan, had no family history of chronic dermatological or other significant diseases, a personal history of mild hypothyroidism, and no recent travel or drug intake. Annular cutaneous lesions appeared on the right thigh and spread to trunk and both limbs within 15 days. Face, hair, nails and palmoplantar sites were spared; mucosa was involved (genital localization). Lesions showed no extension or grouping after onset. Clinically, they were brown-violet macules-to-plaques with well-demarcated borders, ranging from 1 to 3–4 cm. Patient was asymptomatic except mild pruritus of the glans; notably, the distinctive genital lesions raised the primary diagnostic suspicion of lichen planus. Dermoscopy showed well-demarcated plaques with brownish coloration, whitish-gray margins, fine scaling, lighter centers and peppering-like pattern on thigh and trunk. Histology showed compact orthokeratosis, focal hypergranulosis, vacuolar alteration at dermoepidermal junction, edema, dilated vessels, moderate band-like perivascular lymphocytic infiltrate and papillary dermal thickening, consistent with ALP.
Conclusions. This case represents an exceptionally rare eruptive ALP with widespread involvement and prominent genital lesions. Given the scarcity of ALP cases, especially eruptive forms, this report adds clinical and histopathological data to the limited literature. In conclusion, typical genital lesions originally prompted suspicion of lichen planus, while the combination of widespread localization, classic morphology, dermoscopic peppering and histopathological findings strongly supported and confirmed the diagnosis.