Dermoscopy of Perforating Lichen Nitidus: A Case Report
Perforating dermatoses represent a group of skin disorders characterized by papulonodular rashes that involve the elimination of endogenous or exogenous materials through the epidermis. This group includes primary conditions such as reactive perforating collagenosis, elastosis perforans serpiginosa, Kyrle disease, perforating folliculitis, and acquired perforating dermatosis. Additionally, the perforating phenomenon can occur secondary to other skin diseases, including calcinosis cutis, granuloma annulare, chromoblastomycosis, lichen planus, lichen striatus, and, rarely, lichen nitidus. This case report describes a rare instance of extensive perforating lichen nitidus in a Chinese patient, highlighting its clinical, dermoscopic, and histopathological features.
The patient was a 10-year-old boy who presented with asymptomatic lesions on his trunk and upper limbs that had been progressively increasing for two years. He had no significant medical or family history. Clinical examination revealed numerous discrete, flesh-colored, shiny papules measuring approximately 2 mm in diameter. These lesions were distributed over the upper extremities, trunk, lower jaw, and nape, with some papules appearing umbilicated. The oral mucosa, genital area, and nails were not involved, and the Koebner phenomenon was absent.
Dermoscopy of the lesions on the arm revealed a distinctive pattern characterized by three concentric areas. The central area displayed a whitish-brownish hue with a keratin plug. Surrounding this was a structureless whitish annular cloud-like area, and the outermost region featured a peripheral halo with delicate brown pigmentation. This dermoscopic finding was crucial in differentiating perforating lichen nitidus from other dermatoses.
Histopathological examination of an umbilicated papule provided further diagnostic insights. The biopsy showed a well-circumscribed lymphohistiocytic infiltrate located immediately beneath an atrophic epidermis. The adjacent rete ridges appeared to clutch the infiltrate in a “ball-in-claw” configuration. Additionally, degenerated keratinaceous material mixed with lymphohistiocytic cells was observed extending into the stratum corneum through a broad perforating channel. These histopathological features confirmed the diagnosis of perforating lichen nitidus.
The patient was treated with topical corticosteroids for two weeks, which resulted in slight improvement of the lesions. However, the lesions relapsed after discontinuation of the treatment. This case underscores the challenges in managing perforating lichen nitidus, particularly in achieving long-term remission.
Perforating lichen nitidus was first described by Bardach in 1981. Since then, only eleven cases, including the present one, have been reported worldwide. The condition predominantly affects children and young adults, with a higher prevalence in males. Most reported cases involved lesions on the extremities, particularly the dorsal hands, fingers, and feet. Extensive involvement of the trunk, as observed in this case, is exceptionally rare. The present case is the second reported instance of perforating lichen nitidus in the Chinese population and the sixth in the Asian population. The Mongoloid race accounts for half of the reported cases, suggesting that ethnicity may be a risk factor for this condition.
The differential diagnosis of perforating lichen nitidus includes other primary and secondary perforating dermatoses. These conditions share the common pathological process of transepidermal elimination of endogenous or exogenous materials, but the nature of the eliminated materials varies. The exact pathogenesis of perforating dermatoses remains unclear. One theory proposes that altered dermal constituents or foreign bodies bind to unidentified receptors, leading to the formation of transepidermal perforating channels and subsequent extrusion of abnormal dermal components through the epidermis.
Clinically, perforating lichen nitidus must be distinguished from other conditions such as molluscum contagiosum, generalized eruptive syringoma, lichen planus, verruca planae, lichen pilaris, verruciformis epidermodysplasia, steatocystoma multiplex, and follicular eczema. Dermoscopy, a non-invasive diagnostic technique, has proven useful in differentiating perforating lichen nitidus from these other diseases. The dermoscopic features of perforating lichen nitidus include two concentric areas: a central light-brown keratin plug and a peripheral whitish annular cloud-like area. In the present case, an additional outermost halo with delicate brown pigmentation was observed, which may be attributed to the different locations of the lesions.
In conclusion, this case report highlights the clinical, dermoscopic, and histopathological characteristics of perforating lichen nitidus, a rare dermatological condition. The findings underscore the importance of dermoscopy in the diagnostic process and the challenges in managing this condition. Further research is needed to better understand the pathogenesis of perforating dermatoses and to develop more effective treatment strategies.
doi.org/10.1097/CM9.0000000000001011
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