A Florid, Tiny, Discrete Eruption on the Penis FREE

A 13-year-old boy presents for evaluation of asymptomatic papuleson his penis for the past month. The number of lesions has increased slowly. He reports no other associated systemic symptoms and neither a preceding sexual exposure nor a history of sexually transmitted disease. A viral infection was suspected in medical clinics, but no improvement was observed after treatments. Clinical examination reveals many tiny, smooth, translucent, and shiny skin-colored papules affecting nearly all the glans penis and prepuce (Figure). A few similar lesions are distributed on the thighs.

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Lichen nitidus

A. Do nothing; the rash usually resolves over time

The key clinical features to recognize in this case are the tiny, glistening, flesh-colored to pink, dome-shaped papules, which are characteristic of lichen nitidus. Because lichen nitidus usually resolves spontaneously without residual atrophy or pigmentary changes along with its asymptomatic nature, clinical observation becomes a reasonable treatment option. Familiarity with the characteristic manifestations of lichen nitidus, as shown in the Figure, may prevent misdiagnosis as viral infection and avoid unnecessary investigative diagnostic procedures or therapy-related complications.

Lichen nitidus is an inflammatory dermatosis composed of 1- to 2-mm glistening, skin-colored to slight pink papules.¹ The most frequently affected sites are the forearms, abdomen, chest, buttocks, and penis.^2- 3 The causes of lichen nitidus are still unknown.^2- 3 Although lesions are usually discrete, they can be grouped and only rarely do they coalesce.³ Lichen nitidus most commonly affects children and young adults, with a median age of 7 years in boys and 13 years in girls.⁴ Lichen nitidus is typically asymptomatic but can be associated with pruritus.³ Biopsy may sometimes be helpful if lichen nitidus is demonstrated with linear or generalized distribution and atypical keratodermic, petechial, and vesicular-hemorrhagic features or involving palms, soles, and mucosal membranes.³ Histopathologically, lichen nitidus presents as a well-circumscribed lymphohistiocytic infiltrate in a “claw clutching a ball” pattern in the papillary dermis.^3,5

Lichen nitidus on the penis can be confusing to physicians and is often treated as a cutaneous viral infection, such as condyloma acuminatum. Many penile lesions also mimic lichen nitidus and should thus be differentiated; these include pearly penile papules, molluscum contagiosum, herpetic infection, nodular scabies, and bowenoid papulosis. Pearly penile papules mainly affect the coronal sulcus with a ring-like distribution without spreading to the nearby glans penis, penile shaft, prepuce, scrotum, and trunk. Molluscum contagiosum produces papules with characteristic central umbilication. Warts or condyloma typically present with a verrucous surface or cauliflower-like appearance. Herpetic lesions usually demonstrate grouped vesicles arising from an erythematous base, and, in addition to tiny vesicles, some of the lesions may be crusted or erosive. Scabies lesions are highly pruritic red or brown papules. Bowenoid papulosis usually presents as small red, brown, or flesh-colored flat or warty lesions most commonly on the shaft of the penis, which are different from those of lichen nitidus in color and morphology.

Because lichen nitidus is usually asymptomatic and resolves without sequelae, treatment is usually unnecessary.³ Even so, patients or their parents are often anxious and are concerned about the appearance of lichen nitidus, especially when numerous lesions develop on the genital areas. In patients with protracted pruritus, or in whom daily activities and appearances are affected by the appearance of lichen nitidus, topical corticosteroids can be considered as first-line treatment.^1,5- 7 Other therapeutic modalities have been reported as effective, including systemic corticosteroids, antihistamines, itraconazole, acitretin, topical tacrolimus, and UV therapy.^1,4- 8

Familiarity with the characteristic manifestations of lichen nitidus may help clinicians relieve anxiety in patients and avoid unnecessary therapy. If the diagnosis of lichen nitidus is uncertain, the only way to be certain is to perform a biopsy. In this case, the boy's parents did not agree to a biopsy.

At 8-month follow-up, the number of lesions on the glans penis and thighs decreased without treatment.