Shiny, skin-colored, pinhead-sized grouped papules on a young boy

Lichen nitidus is a rare chronic inflammatory rash of multiple small papules that affects individuals of any race or age but is more prevalent in children and young adults.1 It is self-limited and resolves in months to years. The exact...

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Lichen nitidus is a rare chronic inflammatory rash of multiple small papules that affects individuals of any race or age but is more prevalent in children and young adults.¹ It is self-limited and resolves in months to years.

The exact cause of lichen nitidus remains unknown, ² and no infectious agent that precipitates the rash has been identified. There is debate regarding its relationship to lichen planus and whether they represent different immunologic responses to a shared triggering event, given their occasional coexistence on the same patient.¹

Clinically, lichen nitidus is a skin eruption characterized by shiny, flat-topped, skin-colored, pinhead-sized papules arranged in groups and found on the chest, abdomen, genitalia, and upper extremities. The lesions also present along lines of trauma as a result of Koebner phenomenon. These lesions are typically asymptomatic, although pruritus sometimes occurs.^1-5 Hypopigmented papules are also common, especially in patients with darker skin.¹ As the lesions resolve, they are replaced by postinflammatory hyperpigmented macules that also eventually clear.²

Less frequently, lichen nitidus presents with nail changes,³ mucosal involvement,^1,2 or palmoplantar hyperkeratosis.⁴ It is not associated with any systemic diseases, although some maintain that the rare occurrence of widespread lichen nitidus can be an early sign of inflammatory bowel disease, especially Crohn’s disease. Thus, a detailed review of systems is necessary in the context of a diffuse eruption.⁵ In the rare event that lichen nitidus presents with oral involvement, minute flat gray-white papules on the buccal mucosa may be seen.²

Onychodystrophy is seen in a minority of cases of lichen nitidus (<5%-10%) and often precedes the skin manifestations. The lack of skin findings may delay diagnosis. 
Nail changes include thickening, ridging, pitting, or detachment.² The clinician should suspect lichen nitidus with violaceous or pigmentary changes of the nail fold and subtle papules on the affected digits. Patients with lichen nitidus of the nails are more likely to have palmar involvement as well.^3,4

In rare cases, nail lesions associated with lichen nitidus can present as a median canaliform dystrophy, which is a tree-like split in the nail plate; this presentation is associated with isotretinoin use and nailbed tumors. Lichen nitidus should be suspected as a possibility in any child with onychodystrophy or median canaliform dystrophy without a history of trauma, isotretinoin use, or subungal tumor.³ Lichen planus more commonly presents with nail changes (10%), but the changes are typically more severe than those seen in lichen nitidus and may exhibit anonychia or pterygium formation.

Like the skin lesions that occur, the nail findings of lichen nitidus are self-limited.^1-3

Palmar lichen nitidus, although rare, can present as dome-shaped, erythematous, hyperkeratotic, purpuric, or pitted eruptions in the context of lichen nitidus occurring at other sites as well. Palmar lesions may resemble dyshidrotic eczema in some cases. If the papules are pitted or large enough to form plaques, the clinician should rule out arsenical keratosis, Darier disease, nevoid basal cell carcinoma syndrome, and porokeratotic eccrine ostial and dermal duct nevus. When the lesions exhibit hyperkeratosis, consider chronic eczema or keratodermas as well. Unlike skin lesions, palmar lichen nitidus exhibits a chronic course in many patients and may remain refractory to treatment with topical steroids alone or with tacrolimus and acitretin. Palmar lichen nitidus may be difficult to distinguish from lichen planus on examination alone.⁴

In general, the differential diagnosis of lichen nitidus includes lichen planus, lichen striatus, guttate lichen sclerosus, lichen spinulosus, lichen scrofulosorum, verruca plana, papular sarcoidosis, lichenoid secondary syphilis, frictional lichenoid dermatitis (on the elbows and knees), and eczema.^1,3-5 Patient history and clinical findings alone can distinguish lichen nitidus in most cases.

The most difficult diagnosis from which to differentiate lichen nitidus is early lichen planus, as lesions identical to lichen nitidus appear on 25% to 30% of patients with lichen planus.¹ Features indicating a diagnosis of lichen nitidus include monomorphic, monochromatic papules and absence of Wickham striae.¹

If clinical findings are unclear, the unique histologic appearance of lichen nitidus confirms the diagnosis. A focal inflammatory infiltrate closely apposes the epidermis and is surrounded by elongated epidermal rete ridges on the margins, giving the appearance of a claw clutching a ball. The lesion rarely spans more than 2 to 3 dermal papillae.^1-6 The infiltrate is composed of lymphocytes, epithelioid cells, and occasional histiocytes.^1,2,6 Parakeratotic caps are frequently present in the overlying atrophic epidermis and are helpful in differentiating lichen nitidus from early, small lesions of lichen planus. Furthermore, lichen nitidus lacks deposits of immunoreactants, a feature that may be seen in lichen planus.¹

No treatment is required in most cases of lichen nitidus; reassurance of the patient or parent is usually sufficient.^1-4 If the patient is symptomatic or if lesions are generalized or disturbing to the patient cosmetically, several treatment modalities are available, all with varying success rates.² Topical corticosteroids and oral antihistamines can alleviate pruritus. Topical calcineurin inhibitors have been used successfully in some reports of children with lichen nitidus. If topical therapies fail and lichen nitidus recurs or becomes generalized, narrowband ultraviolet B treatment and photochemotherapy are also options.^1,2

The mother of the patient in our case was reassured that the lesions would resolve without treatment, and no treatment was prescribed.


Eman Bahrani, BA, is a medical student and Jennifer S. Ruth, MD, is a dermatology resident at Baylor College of Medicine in Houston.


References


1. Schwarz T. Immunology. In: Bolognia JL, Jorizzo JL, Schaffer JV, eds. Dermatology. 3rd ed. Philadelphia, PA: Elsevier Saunders; 2012:198-199.

2. Chu J, Lam JM. Lichen nitidus. CMAJ. 2014;186(18):E688.

3. Tay EY, Ho MS, Chandran NS, Lee JS, Heng YK. Lichen nitidus presenting with nail changes—case report and review of the literature. Pediatr Dermatol. 2015;32(3):386-388. 

4. Cakmak SK, Unal E, Gönül M, Yayla D, Ozhamam E. Lichen nitidus with involvement of the palms. Pediatr Dermatol. 2013;30(5):e100-e101.
5. Wanat KA, Elenitsas R, Chachkin S, Lubinski S, Rosenbach M. Extensive lichen nitidus as a clue to underlying Crohn’s disease. J Am Acad Dermatol. 2012;67(5):e218-e220.
6. Liu H, Chen S, Shi Z, Zhang F. In vivo imaging of lichen nitidus with confocal laser scanning microscopy. Arch Dermatol. 2011;147(1):142.