Lichen nitidus

 

 

 

Salient features

 

·       The eruption consists of multiple, tiny, discrete, shiny papules, often in clusters

 

·       Favored sites of involvement include the flexor aspects of the upper extremities, the genitalia, and the anterior trunk

 

·       Linear arrays of papules occur secondary to the Koebner phenomenon

 

·       The histologic correlate of the papule is a well-circumscribed infiltrate composed of lymphocytes and epithelioid cells confined to the width of two to three dermal papillae

 

 

Introduction

 

Lichen nitidus is an uncommon chronic eruption consisting of multiple, tiny, discrete, skin-colored papules that are often arranged in larger clusters. The papules have a distinctive histology with a dense, well-circumscribed, lymphohistiocytic infiltrate closely apposed to the epidermis. It is generally accepted that lichen nitidus has no relationship to any systemic illness. Only a few authors believe that it may be a cutaneous manifestation of Crohn disease. Lichen nitidus is more prevalent among children or young adults, and a female predominance has been described in the generalized variant.

 

Clinical Features

Lichen nitidus is characterized by numerous tiny, uniform pinpoint to pinhead-sized round papules, which are usually asymptomatic and skin‐colored, with a flat, shiny surface; occasionally they have a central depression. They usually remain discrete, although they may be closely grouped. There may be pruritus, but it is an uncommon feature. Although most often skin-colored, the papules can exhibit a variety of hues, from pink or yellow to red–blue or brown. In darkly pigmented individuals, the papules tend to be hypo pigmented, but sometimes they are hyper pigmented; marked hyper pigmentation has rarely been reported.

They are found on any part of the body but the sites of predilection are the flexor aspects of the upper extremities, the genitalia (glans and shaft of the penis), dorsal aspects of the hands and the anterior trunk (chest, lower abdomen). Less commonly, the face, neck, and lower extremities are involved. Oral lesions are rare. Nail involvement is observed in up to 10% of patients (primarily adults) and the changes include pitting, rippling, longitudinal ridging, terminal splitting, and increased longitudinal linear striations.

 

Lichen nitidus is one of several diseases that exhibit the Koebner phenomenon where linear arrays of papules are seen. Vesicular and hemorrhagic lesions are found in some patients, and they are often admixed with the more typical papules. Several other clinical variants have been described, including palmoplantar and follicular spines. A perforating variant has also been reported, usually in association with LP. The eruption is sometimes generalized and in this form, lesions occasionally coalesce. According to one study, the duration in two-thirds of the patients was 1 year or less and the longest duration was 8 years.

 

 

Comparison of clinical and histologic features of lichen nitidus versus lichen planus
	Lichen nitidus	Lichen planus
Incidence                  Rare                                   common   Clinical
Size     Shape	Pinhead     Round	Pinhead to larger plaques   Polygonal
Color	Skin-colored	Violaceous
Number	Multiple to numerous	Multiple
Distribution	Upper extremities (flexor aspects), genitalia, chest, abdomen	Wrists, flexor forearms, presacral area, dorsal hands, shins, genitalia
Oral involvement	Rare	Common (>50%)
Nail involvement	<5–10%	∼10%
Wickham striae	Absent	Common
Hyperpigmentation	Uncommon	Common
Hypopigmentation	Common†	Unusual
Koebner phenomenon	Common	Common
Pruritus	Sometimes	Common
Histologic
Parakeratotic cap	Common	Rare
Granular layer	Thin to absent	Focally increased
Dermal infiltrate	Lymphocytes, epithelioid cells, and occasional Langhans giant cells; usually confined to width of 2–3 dermal papillae; “ball and claw” configuration due to hyperplastic rete ridges	Band-like infiltrate of lymphocytes
Trans epidermal elimination	Unusual	Rare
Deposits of immunoreactants	Absent	Globular deposits of IgG, IgA, IgM, and/or C3 in the papillary dermis

 

† Especially in darkly pigmented individuals.

 

Differential diagnosis

 

Lichen nitidus must be distinguished from lichen scrofulosorum, where there are follicular papules grouped in small patches on the trunk, and from keratosis pilaris, where there are horny follicular papules mainly on the extensor surface of the limbs. In cases of doubt, a biopsy usually clarifies the diagnosis. It is not always possible to differentiate early tiny papules of LP because they may be clinically and histologically indistinguishable from lichen nitidus. Furthermore, lesions identical to lichen nitidus can be found in 25% to 30% of patients with LP. In such cases, the lack of variation in size, the absence of a violaceous color or Wickham striae, and no deposits of immunoglobulin in dermal papillae would suggest the diagnosis of lichen nitidus.

 

 

Histology

 

The constellation of histologic features in lichen nitidus is very distinctive. As a result, the clinical diagnosis can be confirmed histologically. The histology of a typical papule is characteristic, with a well-circumscribed infiltrate composed of lymphocytes, epithelioid cells and occasional Langhans giant cells confined to the width of two to three dermal papillae closely apposed to the atrophic epidermis is typically “clutched” by the surrounding hyperplastic rete ridges in a “ball and claw” configuration.  The overlying epidermis is usually atrophic and frequently exhibits a parakeratotic “cap” centrally. Absence or thinning of the overlying granular layer is seen and vacuolar degeneration of the basal layer is consistently observed, often accompanied by incontinence of melanin pigment. Civatte bodies are occasionally seen. A Max-Joseph-like space, i.e. focal separation of the epidermis and dermis secondary to vacuolar degeneration, is sometimes observed. The lichenoid infiltrate closely apposes the epidermis and is thought to play a role in inducing reactive epidermal hyperplasia of the surrounding rete ridges. In perforating lichen nitidus, transepidermal elimination is observed.   Treatment   Because the disease is asymptomatic and self-limiting, no treatment is required in most cases. Treatment of lichen nitidus is warranted when it is associated with protracted pruritus, become generalized or for lesions in cosmetically sensitive areas. Topical fluorinated glucocorticoids are first line treatment for LN and may yield favorable results. Tacrolimus ointment is a second line treatment for body and first line treatment for facial and intetriginous disease and is effective after 1 month of therapy. A short course of oral glucocorticoids may also be helpful and hasten resolution of more extensive, generalized, or symptomatic disease. Narrowband UVB could be a safe and effective treatment in generalized lichen nitidus. Oral retinoids is an effective treatment in palmoplantar type. ++History of exposure to tuberculosis in the setting of lichen nitidus should be investigated and, when appropriate, treated with antituberculous medications. Low-molecular-weight heparin was used safely and successfully at weekly dose of 3 mg subcutaneously. + Treatment of Lichen Nitidus   Topical Physical Systemic First line Topical steroids Sun protection for actinic type Narrowband UVB (generalized) Antihistamines(pruritu) Second line           3rd line Topical tacrolimus (1st line Rx on face and intertriginous areas & 2nd line Rx for elsewhere) UVA and UVB phototherapy (generalized)             Psoralen plus UVA Oral steroids 0.3mg/kg/day (generalized & symptomatic) Oral acetretin (palmar) Cyclosporine 4 mg/kg/day(generalized & symptomatic)   Itraconazole( generalized) Antituberculous agents-INH (positive PPD result)   Enoxaparin Sodium 3 mg SC weekly (generalized)