CASE #2: Lichen striatus

Lichen striatus is a common entity that may be confused with an epidermal nevus. However, lichen striatus is not present at birth and is associated with spontaneous resolution over time. On histology, there is less hyperkeratosis and acanthosis with more dyskeratosis, spongiosis and lichenoid inflammation.9

Nevus sebaceus usually occur on the head (instead of the trunk); however, it can also have a verrucous appearance and is considered a subtype of an epidermal nevus with sebaceous and apocrine gland hamar­tomatous components. If the epidermal nevus is small in size, it must be differentiated from a seborrheic keratosis, verruca vulgaris or psoriasis.



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Multiple or extensive epidermal nevi in an infant or child may be a sign of systemic abnormalities. A strong working relationship between the patient, parent, dermatologist and pediatrician is necessary to diagnose and treat the disorder properly. The clinician should perform a thorough history and physical examination to screen for any signs that may be a prelude to the diagnosis of epidermal nevus syndrome.

Surgical removal of the lesion by curettage or shave excision is common.10 However, these surgical modalities generally remove only the epidermis, so recurrence is not unexpected, and the patient usually needs repeated procedures to minimize the appearance of the epidermal nevus.

Full-thickness surgical excision is another option for localized and small epidermal nevi and often leads to resolution. However, hypertrophic and keloidal scars are common. Chronic retinoid therapy has been found to be effective in reducing the thickness of ichthyosis hystrix but does not result in complete resolution.5 The risks and benefits of treatment must be discussed prior to the initiation of therapy. Laser ablation as been attempted but frequently results in scars that may not be cosmetically acceptable to the patient. Other topical treatments that have been used with some benefit include corticosteroids, tars, anthralin, 5-fluorouracil and podophyllin.5

Most patients who are diagnosed with an epidermal nevus will have no complications. Depending on the location, cosmesis may be an issue. If it is, any of the above modalities may be attempted. With more extensive epidermal nevi, the clinician must worry about the diagnosis of epidermal nevus syndrome, which may lead to systemic complications. These nevi are also more difficult to treat and can cause great distress cosmetically. 


This patient was treated with a shave excision in an attempt to improve the cosmetic appearance and minimize the risk of scarring. She was informed that this was not being done to remove the epidermal nevus but would likely improve the cosmetic appearance. The patient was advised of the likely need for further treatment in the future, as recurrence of the nevus is common. She was also given a trial of tazarotene (Tazorac) 0.05% cream to be used at bedtime as tolerated.


Lichen striatus was first described as a peculiar linear papular eruption and named lichenoid trophoneurosis by Balzer and Mercier in 1898. It would not be until 1938 that Senear and Caro implemented the current name, lichen striatus.5

Lichen striatus is an uncommon, asymptomatic, self-limited linear and lichenoid dermatosis. Skin is the only organ affected, and the lesions primarily occur on the extremities.11,12 On occasion, the face, trunk and buttocks may also be affected.

In most cases, the age of onset is anywhere from 4 months to approximately 15 years. The vast majority of cases occur in preschool-aged children, and the median age of onset is 2 to 3 years. There have been occasional case reports of the disorder occurring in adults. The female-to-male ratio is approximately 2:1.13 The eruption is usually asymptomatic and takes a few weeks to months to reach the full clinical appearance. 


Lichen striatus is classified as a mosaic condition because it tends to follow Blaschko’s lines, which are thought to trace the embryologic development of skin. However, the genes involved are unknown, as are the triggers for the disorder. Seasonal prevalence in the spring and summer months has led to examination of environmental factors, viruses and toxic agents.1

The prevailing theory holds that during early fetal development, abnormal clone epidermal cells produced by somatic mutations will migrate out along the lines of Blaschko. During this time, any exposure to such infectious agents as a virus could break previous tolerance to the clone by bringing to mind a novel membrane antigen. Clustered or scattered CD8+ T-cells found around necrotic keratinocytes support a cell-mediated immunologic reaction by which cytotoxic T-cells would attack and eliminate the mutated or virally modified keratinocytic clones.8 This causes the characteristic lesions of lichen striatus. It is also though that the disorder may represent a manifestation of an atopic diathesis or be the cause of an infectious agent in genetically predisposed individuals. 


The lesions range from 2 to 4 mm in diameter and may be flat-topped, smooth or scaly. The lesions are often clustered in a discrete band that may be continuous or interrupted and often measures 1 to 2 cm in width. Lesions may be seen as skin-colored, pink or tan papules. The lesions are usually in a unilateral streak along Blaschko’s lines and are located mainly on the extremities.

Occasionally, they may be seen in a bilateral distribution pattern or in parallel bands. Uncommonly, lichen striatus may involve the trunk, head or neck. There are reports of the disorder spreading proximally from an extremity to the trunk or distally from the trunk to an extremity.5 


Although lichen striatus is usually asymptomatic, the condition can be associated with severe pruritus. The lesions take weeks to months to fully develop and often resolve spontaneously within months to years after onset. Once the lesion resolves, a postinflammatory hypopigmentation can occur. This is more common in darker-skinned individuals. Total nail loss can result if the lesion spreads to the nail apparatus. Onycholysis, splitting and fraying may also occur.5 While lichen striatus does not usually recur, if a relapse is seen, it may strike at the same site or on the same side of the body.8

The histopathologic examination of lichen striatus is variable and depends on the age of the lesion at the time of the biopsy. Spongiosis, exocytosis, parakeratosis, dyskeratosis, and focal or diffuse lysis of the basal layer are all alterations that may be seen within the epidermis.8 In the dermis, there is a superficial perivascular or lichenoid (bandlike) inflammation with a variable number of histiocytes and lymphocytes.14 This infiltrate may extend into the epidermis in areas where there are necrotic keratinocytes and vacuolar alteration of the basal layer.15 If the inflammatory infiltrate is seen in the reticular dermis around hair follicles and eccrine glands, this may help to make the diagnosis of lichen striatus.8 Plasma cells and eosinophils are rarely seen. Older lesions may appear similar to lichen nitidus or lichen planus. 


The main differential diagnoses for lichen striatus are those inflammatory diseases that are linear in nature, including linear lichen planus, blaschkitis and linear graft-versus-host disease.5 Linear lichen planus and lichen striatus are two disorders that may be hard to distinguish histologically, thus careful clinical observation is needed to differentiate the two.1,8

The primary lesions often differ in size and color; hypopigmentation is often the by-product of lichen striatus, whereas hyperpigmentation occurs during the course of linear lichen planus. Lichen striatus also resolves spontaneously and often does not need treatment. Blaschkitis is usually seen on the trunk of adults as multiple streaks that have features of dermatitis. Other differential diagnoses to consider are linear Darier disease, linear inflammatory verrucous epidermal nevus, linear psoriasis and linear porokeratosis.5 When the diagnosis is in question, a histopathologic examination of a cutaneous biopsy will help differentiate lichen striatus from most other linear eruptions. 


Lichen striatus will usually resolve spontaneously within three to 12 months, and patients and parents should be reassured.9 Topical corticosteroids and oral antihistamines may be used to treat symptoms of intense pruritus. Topical corticosteroids (under occlusion) or calcineurin inhibitors have been shown to be effective at accelerating the resolution of the lesions in sporadic case reports.5 Resolution of lichen striatus usually goes without incident. However, the area may be hypopigmented once the lesion is resolved, but even this will disappear over time. 


This patient was given reassurance that the lesion would resolve within months to years with no complications.

Kerri Robbins, MD, is a resident in the department of dermatology at Baylor College of Medicine in Houston. The author has no relationships to disclose relating to the content of this article.


References


1. Paller AS, Mancini AJ. Hurwitz Clinical Pediatric Dermatology. 3rd ed. Philadelphia, Pa.: Elsevier Saunders; 2006:216-217, 71-72.


2. Alsaleh QA, Nanda A, Hassab-el-Naby HM, Sakr MF. “Familial inflammatory linear verrucous epidermal nevus (ILVEN).” Int J Dermatol. 1994;33:52-54.


3. Goldman K, Don PC. “Adult onset of inflammatory linear verrucous epidermal nevus in a mother and her daughter.” Dermatology. 1994:189:170-172. 


4. Rogers M, McCrossin I, Commens C. “Epidermal nevi and the epidermal nevus syndrome. A review of 131 cases.” J Am Acad Dermatol. 1989;20:476-488.


5. Bolognia JL, Jorizzo JL, Rapini RP eds. Dermatology, 2nd ed. St. Louis, Mo.: Elsevier-Mosby; 2008:1671-1672, 170-172.


6. Loff HJ, Bardenstein DS, Levine MR. “Systematized epidermal nevi: case report and review of clinical manifestations.” Ophthal Plast Reconstr Surg. 1994;10:262-266.


7. Fitzpatrick TB, Johnson RA, Wolff K, Suurmond R eds. Color Atlas and Synopsis of Clinical Dermatology, 5th ed. New York, N.Y.: McGraw-Hill; 2005:214-215.


8. Elder DE, Elenitsas R, Johnson BL et al eds. Lever’s Histopathology of the Skin. 10th ed. Philadelphia, Pa.: Lippincott Williams & Wilkins; 2009:88, 103-106, 690, 110-111, 193-194.


9. RP Rapini. Practical Dermatopathology. Philadelphia, Pa.: Elsevier Mosby; 2005:233-234.


10. Dellon AL, Luethke R, Wong L, Barnett N. “Epidermal nevus: surgical treatment by partial-thickness skin excision.” Ann Plast Surg. 1992;28:292-296. 


11. Kennedy D, Rogers M. “Lichen striatus.” Pediatr Dermatol. 1996;13:95-99.


12. Taieb A, el Youbi A, Grosshans E, Maleville J. “Lichen striatus: a Blaschko linear acquired inflammatory skin eruption.” J Am Acad Dermatol. 1991;25:637-642.


13. Patrizi A, Nevi I, Fiorentini C et al. “Lichen striatus: clincal and laboratory features of 115 children.” Pediatr Dermatol. 2004;21:197-204. 


14. Reed RJ, Meek T, Ichinose H. “Lichen striatus: a model for the histological spectrum of lichenoid reactions.” J Cutan Pathol. 1975; 2:1-18.


15. Gianotti R, Restano L, Grimalt R et al. “Lichen straitus — a chameleon: a histopathological and immunohistological study of 41 cases.” J Cutan Pathol. 1995;22:18-22.