Dermatology

Lichen Spinulosus (Keratosis Spinulosa)

Are You Confident of the Diagnosis?

What you should be alert for in the history

Characteristic findings on physical examination

Lichen spinulosus is a rare dermatosis that typically presents in children to young adults as asymptomatic, but at times mildly pruritic, small flesh-colored follicular keratotic spiny papules, usually arranged in plaque-like 2 to 6cm symmetric groups on the neck, lateral thighs and buttocks, abdomen, knees, and extensor upper extremities (Figure 1). The lesion spines are characteristically tiny and “nutmeg grater"-like, and when removed, they leave behind a tiny conical orifice.

Figure 1.

Lichen spinulosus

Expected results of diagnostic studies [histopathology, serologic tests, genetic tests, imaging studies]

Histopathologic examination of lichen spinulosus shows orthoparakeratotic plugging of the dilated follicular infundibulum with a mononuclear perivascular and perifollicular lymphocytic infiltrate (Figure 2).

Figure 2.

Lichen spinulosus, low power. Orthoparakeratotic plugging of the dialated follicular infundibulum.

Diagnosis confirmation

The clinical differential diagnosis includes other lichenoid eruptions, but it is more commonly grouped as part of the family of follicular keratotic disorders, including Darier disease (keratosis follicularis) and keratosis pilaris. In fact, some consider lichen spinulosus to be a variant of keratosis pilaris, and its ICD-9 code is categorized with keratosis pilaris instead of the lichenoid disorders.

Keratosis pilaris is vastly more common (present in up to 40% of children) than lichen spinulosus and occurs in broader, more poorly-defined areas of the upper arms and legs compared to the discrete groupings of lichen spinulosus. The lesions of Darier disease and pityriasis rubra pilaris can focally resemble lichen spinulosus, but generally, they have a more diffuse and polymorphic lesion pattern depending on body site. For instance, Darier lesions can appear more verrucal in frictional areas, and truncal pityriasis rubra pilaris lesions can be more inflammatory with classic islands of sparing.

An entity called frictional lichenoid eruption can also resemble lichen spinulosus, but lesions are specifically triggered by frictional force in children while playing, distributed in places like the knees and elbows, and they resolve when the friction ceases. Lichen spinulosus can be distributed in frictional areas, but there is no evidence that it truly koebnerizes. Lichen planopilaris lesions can sometimes clinically mimic lichen spinulosus, but its distribution on the scalp, inflammatory and scarring nature, polymorphic eruptions on the body when part of the Graham-Little syndrome, and disparate lichenoid follicular and scarring histopathologic findings would easily distinguish it from lichen spinulosus.

On biopsy, keratosis pilaris and pityriasis rubra pilaris can appear identical to lichen spinulosus. Similarly to lichen planus, lichen spinulosus displays linear IgM basement membrane deposition on immunohistochemistry, but lichen spinulosus lacks colloid body accentuation.

Who is at Risk for Developing this Disease?

Lichen spinulosus typically presents in children and young adults, and in most studies, it occurs in males slightly more commonly than females. It appears equally in all races, and no consistent genetic or inheritance pattern has been identified.

What is the Cause of the Disease?

Etiology

Pathophysiology

The etiology and pathophysiology of lichen spinulosus are unknown, but some surmise a link with immune alterations typically associated with atopy and hyperkeratotic disorders, such as the lectin pathway. Also, hypotheses exist that link the disorder to microorganisms, in that the eruption occurs due to an immune response to hair follicular organisms like pityrosporum.

Systemic Implications and Complications

There are no consistent systemic associations with lichen spinulosus. Small series and isolated reports note possible links to atopy, HIV, alcoholism, acne conglobata, Hodgkin's lymphoma, Crohn's disease, heavy metal ingestion (gold, thallium), and infectious conditions like syphilis, lichen scrofulosorum, and a mycotic id reaction.

If the eruption is more generalized, these associations (particularly HIV) are more common and correlate with a later age of onset. Lichen spinulosus does not typically warrant a systemic workup in the absence of other systemic symptoms or risk factors, however.

Treatment Options

Treatment options are summarized in the Table I.

Table I.

Treatment options for lichen spinulosus
Medical Treatment Surgical Procedures Physical Modalities
Topical:Salicylic acidLactic acidUreaTretinoinPropylene glycolTarVitamin D analoguesCorticosteroids No surgical therapies reported Hydroactive adhesives
No systemic therapies reported  

Optimal Therapeutic Approach for this Disease

The clinical course of lichen spinulosus is variable, with many cases tending toward spontaneous resolution. Therefore, if asymptomatic, the first option could be observation/no treatment. If treatment is sought, topical therapy, including keratolytics and emollients, is most effective.

Topical salicylic acid 6% gel has been the most reported therapy, administered nightly under occlusion for 2 weeks, or without occlusion for 8 weeks, with typical complete clearance of lesions. However, some have reported recurrence and necessary maintenance therapy twice weekly.

Because pediatric patients can be at risk for salicylism due to their large surface area to volume ratio, prolonged use, particularly under occlusion, can be risky. Specifically, salicylic acid in greater than 5% concentrations should not be used in children under 12 years of age and should be implemented cautiously in any patients with liver and kidney disease or those who have extensive body surface area involvement of their skin disease or erythroderma.

Therefore, other keratolytics like lactic acid preparations (for example, ammonium lactate cream 5% or 12%), urea 10% lotion, tar preparations, and propylene glycol can be used in similar regimens as above with some success.

Side effects of keratolytics include burning and stinging on application. Retinoids have also been implemented nightly for variable periods of time for lichen spinulosus, although efficacy is variable. A combination therapy including tretinoin 0.04% gel nightly and hydroactive adhesive application (classically used for comedonal acne, Biore® brand strips for example) daily for 1 to 2 months has shown more promise, as it includes mechanical and physiologic means of treatment.

Topical vitamin D analogues, like calcipotriol, calcitriol, and tacalcitol (not available in the United States), have rarely been used, with anithyperkeratotic effects and a typically adverse-event-free course; dosing is usually twice daily without occlusion for 2 to 4 weeks.

Topical steroids have been used with some success in management of pruritus but with little efficacy in ameliorating the keratotic eruption and risk of atrophy with prolonged use. Midpotency preparations, like trimacinalone 01.% cream, twice daily for 2 weeks is a good starting point, but frequency of application, vehicle, and steroid potency will vary based on body site and patient preference, as in atopic regimens.

Patient Management

As mentioned, there is a tendency for lichen spinulosus to spontaneously resolve, sometimes at puberty, sometimes within 1 to 2 years of presentation, but it can also persist for years or remit and recur at random. With treatment, most cases respond within a month or two. With its heterogeneous course, however, the patient may need to halt and restart therapy depending on eruption symptoms and local side effects.

Salicylism, as aforementioned, can ensue in children following salicylic acid application that is diffuse, prolonged, occluded, or applied in particularly absorbent body sites. Although rare, the early symptoms of salicylism would include hyperventilation, nausea, vomiting, diaphoresis, and tinnitus; in older patients, it may merely manifest as mental status changes.

Because lichen spinulosus has a benign course, avoidance of topical salicylates completely may be advised in certain patients (those under 12 years of age, those with kidney or liver disease, and those with extensive skin involvement or erythroderma). Alternatively, specific and appropriate application instructions should be given, and long-term use of or injudicious provision of refills would be ill-advised.

Unusual Clinical Scenarios to Consider in Patient Management

Particularly diffuse skin manifestations of lichen spinulosus may correlate with some systemic comorbidities, like HIV, atopy, and alcoholism, as mentioned. There are reports of skin involvement improving with appropriate HIV therapy, nutritional support and avoidance of alcohol in alcoholics, and excellent daily skin care with mild soaps and bland emollients in atopics.

What is the Evidence?

Boyd, AS. "Lichen spinulosus: case report and overview". Cutis. vol. 43. 1989. pp. 557-60.

(This case and review outlines clinical characteristics, atopic correlation, and treatment modalities, including the usefulness of specialty dermatologic care, for lichen spinulosus.)

Forman, SB, Hudgins, EM, Blaylock, WK. "Lichen spinulosus: excellent response to tretinoin gel and hydroactive adhesive applications". Arch Dermatol. vol. 143. 2007. pp. 122-3.

(The treatment regimen of a topical retinoid with mechanical hydroactive adhesive for lichen spinulosus is outlined.)

Friedman, SJ. "Lichen spinulosus". Clinicopathologic review of thirty-five cases. J Am Acad Dermatol. vol. 22. 1990. pp. 261-4.

(This is the largest available review of lichen spinulosus patient characteristics, clinical morphology, and biopsy findings.)

Kim, SH, Kang, JH, Seo, JK, Hwang, SW, Sun, HS, Lee, D. "Successful treatment of lichen spinulosus with topical tacalcitol cream". Ped Dermatol. vol. 27. 2010. pp. 546-7.

(This case describes the efficacy, pathomechanism, and recommended application schedule of vitamin D analogues in lichen spinulosus.)

Tilly, JJ, Drolet, BA, Esterly, NB. "Lichenoid eruptions in children". J Am Acad Dermatol. vol. 51. 2004. pp. 606-24.

(This is a thorough review of lichenoid dermatoses in children, with tabular comparisons and descriptions, including summaries of clinical, histopathologic, pathogenic, and therapeutic features.)

Tuyp, E, McLeod, WA, Boyko, W. "Lichen spinulosus with immunofluorescent studies". Cutis. vol. 33. 1984. pp. 197-200.

(This study describes the immunofluorescent findings in lichen spinulosus, particularly as it compares to lichen planus.)
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