Diagnosis: Lichen nitidus
This clinical manifestation of multiple, hypopigmented, pinhead-sized papules is most consistent with the diagnosis of lichen nitidus. The linear appearance of the micropapules at sites of trauma or skin pressure (known as the Koebner phenomenon) is a valuable clue in the diagnosis of this skin disorder. In this case, it was most likely the result of the child scratching his skin.
A rare and chronic inflammatory skin condition, lichen nitidus is characterized by numerous small, skin-colored papules that are often arranged in clusters on the upper extremities, the genitalia, and the anterior trunk.1 The papules are less likely to occur on the face, lower extremities, palms, and soles. Oral mucosal and nail involvement are rare. The condition is usually asymptomatic but can sometimes be associated with pruritus.
Lichen nitidus occurs more frequently in children or young adults and has a female predominance.1 It does not exhibit a predilection of any race.2 The etiology and pathogenesis of lichen nitidus remain unclear. Genetic factors have been proposed as a potential cause; it has also been reported to be associated with Down syndrome.3
Making the Dx with dermoscopy, skin biopsy
Dermoscopy is a useful technique for diagnosing lichen nitidus. Dermoscopic features of lichen nitidus include white, well-demarcated circular areas with a brown shadow.4 Skin biopsy provides a definitive diagnosis. Lichen nitidus has a distinct histopathologic “ball and claw” appearance of rete ridges clutching a lymphohistiocytic infiltrate.1
Consider these common conditions in the differential
The differential diagnosis includes lichen spinulosus, papular eczema, lichen planus, keratosis pilaris, and verruca plana (flat warts).
Continue to: Lichen spinulosus