Solitary Porokeratosis of Mibelli at an unusual site

Abstract

Introduction Porokeratosis is an assorted group of five genetic disorders. These include porokeratosis of Mibelli, DSAP, punctate porokeratosis, porokeratosis palmaris et plantaris disseminata, and linear porokeratosis [1]. They are disorders of abnormal keratinization characterized by the appearance of atrophic patches. Porokeratosis of Mibelli is referred to the more localized form of this disorder usually manifesting as solitary or a small group of lesions. It was first described by Mibelli in 1893 who described atrophic patches surrounded by a clinically and histologically unique ridge like border termed the cornoid lamella. The cornoid lamella is formed by rapidly proliferating atypical keratinocytes that expands peripherally to form a raised boundary at the junction of abnormal and normal cells. These lesions are most commonly found on the extremities, but can also be found on genitalia, face, oral mucosa and cornea [2]. Though the patches are generally asymptomatic they can often lead to ulcerative, verrucous, giant, and malignant lesions [3]. We describe a case of Porokeratosis of Mibelli at an unusual site in a 22 yr old male. The presenting history, clinical findings, biopsy results and available literature are reviewed. Case Report A 22 year old male patient came with complaints of a white rash over his nose since 6 months. It was confined to the left ala of the nose (Fig. 1). The lesion started as a small papule and gradually spread peripherally. There was central clearing with hypo pigmentation and a raised border. The patient's history was otherwise insignificant. There was no similar history in the family. He was born of a non consanguineous marriage. There was no history suggestive of photosensitivity. His systemic examination was within normal limits. The differential diagnosis of Discoid Lupus Erythematoses, Basal Cell Carcinoma, Lupus Vulgaris and Porokeratosis were considered. Routine blood investigations were normal. HIV 1 and 2 was non reactive. A full depth skin biopsy was taken from the outer part of the lesion with a 2mm disposable skin biopsy punch and subjected to histopathology. The histopathology revealed foci of epidermal invagination filled with keratin and parakeratotic coronoid lamella. Dermis showed a mild to moderate infiltrate of lymphocytes (Fig. 2). On the basis of history, clinical examination and histopathology, a diagnosis of Porokeratosis of Mibelli was made. Topical tretinoin was prescribed for the management of the lesion.