INTRODUCTION — Lichen striatus is an acquired, asymptomatic, and self-limited linear inflammatory skin disorder that predominantly affects children [1,2]. The eruption is typically unilateral, most often involving the extremities, and follows the lines of Blaschko in a continuous or interrupted pattern. The onset is sudden, with full progression over a few weeks and resolution typically within 6 to 12 months.
This topic will discuss the pathogenesis, clinical manifestations, diagnosis, and treatment of lichen striatus.
EPIDEMIOLOGY — Lichen striatus is a relatively uncommon disease that most frequently occurs in children 5 to 15 years of age. However, it may occur at any age, from early infancy to adulthood [3-8]. Lichen striatus has been reported in all ethnic groups and appears to be more common in females [4,6-8]. There are a few reports of familial cases, many occurring simultaneously [4,9-14].
PATHOGENESIS — The precise etiology of lichen striatus is unknown. Viral infections, trauma, hypersensitivity reactions, vaccines, medications, and pregnancy have been proposed as triggering factors [15-19]. A positive personal or family history of asthma, atopic dermatitis, or allergic rhinitis has been reported in 60 to 85 percent of individuals with lichen striatus, suggesting that atopy may be a predisposing factor [6,20,21].
The distribution of lichen striatus along the lines of Blaschko (lines corresponding to the direction of growth of cutaneous cells during embryogenesis (figure 1)) suggests that lichen striatus is a condition of cutaneous mosaicism, due to somatic (postzygotic) mutations that produce abnormal keratinocyte clones during early embryogenesis. These aberrant clones may remain silent until a triggering event causes a break in immunologic tolerance and initiates an autoimmune response [5,22]. Potential triggers include viral infections, vaccines, trauma, pregnancy, hypersensitivity reactions, and medications [6,10,15-18,23-25].
The immunohistologic finding of CD8+ T lymphocytes surrounding necrotic keratinocytes and activated Langerhans cells suggests that a cell-mediated cytotoxic reaction may be involved in the pathogenesis of lichen striatus [10,22,26]. This reaction may cause the complete or partial deletion of the mutant clone, explaining the rarity of recurrence of lichen striatus. Plasmacytoid dendritic cells have also been seen in lichen striatus, suggesting that they may play a role in pathogenesis. Their presence and perieccrine location may be helpful in distinguishing among other inflammatory conditions, such as lichen planus [27]. (See 'Pathology' below.)
CLINICAL MANIFESTATIONS — Lichen striatus typically presents with a sudden eruption of red, pink, or skin-colored flat-topped papules arranged in a linear band that follows the lines of Blaschko (picture 1A-D). The band is usually narrow, solitary, and unilateral, and may be continuous or interrupted.
The extremities (picture 1C) are most commonly involved, followed by the trunk (picture 1D), buttocks, face (picture 1A-B), and nails (picture 2) [28]. A V-shaped pattern over the spine and S-shaped on the lateral and anterior aspect of the trunk (picture 1D) is characteristic [5,6,29]. Bilateral or multiple bands have also been described (picture 3) [5,30-32].
There are three morphologic variants of lichen striatus [6]:
●Typical lichen striatus – Discrete 1 to 4 mm flat-topped, flesh-colored to erythematous, smooth or scaly papules, and rarely vesicles arranged in a narrow band along the lines of Blaschko (picture 1D and picture 4). This is the most common variant, occurring in approximately 80 percent of patients [6].
●Lichen striatus albus – Hypopigmented macules and/or papules with only a few typical lichenoid pink papules at onset. This variant is more common in darker-skinned patients (picture 5).
●Nail lichen striatus – Lichen striatus of the nail matrix may present as longitudinal ridging or fissuring, splitting, fraying, onycholysis, nail pitting, punctate or striate leukonychia, or nail plate thinning or thickening (picture 2) [25,33-36]. Nail lichen striatus usually involves only one nail and often affects only the lateral or medial portion of the nail plate [34].
Nail involvement is rare and is usually seen in association with typical skin lesions, although cases limited to the nail have been reported [6,34,35]. Nail lesions may precede, follow, or develop concurrently with the skin lesions.
Lichen striatus is usually asymptomatic. Pruritus has been reported in up to one-third of the patients, most often in individuals with atopy [6,8].
Clinical course — On average, the active phase of lichen striatus lasts six months, ranging from less than three months to several years [6,37]. Lesions then resolve spontaneously, leaving a transient postinflammatory hypopigmentation or, rarely, hyperpigmentation. The hypopigmentation resolves slowly in one to three years and is not influenced by treatment [4,5].
Relapses are rare and usually involve the same site or hemibody, with eventual complete clearance. Nail lesions may persist for several years, but eventually resolve without permanent nail dystrophy [6].
DIAGNOSIS — The diagnosis of lichen striatus is usually clinical, based upon the classic finding of erythematous or skin-colored, flat-topped papules arranged in a linear band along the lines of Blaschko (picture 1B-D). If the diagnosis is in question, a skin biopsy may be necessary for histopathologic confirmation. (See 'Pathology' below.)
Dermoscopy can be useful in the clinical diagnosis of lichen striatus of the nail by enhancing the detection of longitudinal nail plate fissures and splitting, red streaks, and erythematous bands disrupting the lunula [38,39]. (See "Nail disorders in infants and children: Acquired nail diseases", section on 'Nail lichen striatus'.)
Pathology — The histopathologic features of lichen striatus are variable and may be nonspecific, depending upon the age of the lesion and area biopsied. However, in the active phase of the disease, there are several distinctive microscopic findings that may support the clinical diagnosis [40]:
●A superficial, band-like, lichenoid infiltrate in the papillary dermis at the dermal-epidermal junction, with focal vacuolar alteration of the basal layer (picture 6)
●A deeper, dermal, lymphocytic infiltrate mainly centered around eccrine glands and hair follicles (picture 7)
●Variable epidermal changes, such as focal spongiosis, exocytosis, patchy hyperkeratosis, parakeratosis, and dyskeratosis
Similar changes can be observed also in lichen striatus of the nail matrix [22,34].
DIFFERENTIAL DIAGNOSIS — Many conditions may mimic lichen striatus, including:
●Blaschkitis – Blaschkitis is an idiopathic, pruritic, papulovesicular eruption, often arranged in multiple broad bands along the lines of Blaschko. It is more often seen in adults, but has been reported also in children [26,41]. Blaschkitis has a sudden onset with rapid resolution and frequent relapses. On histopathology, blaschkitis tends to have a predominately spongiotic pattern, in contrast to the lichenoid pattern of lichen striatus.
●Inflammatory linear verrucous epidermal nevus – Inflammatory linear verrucous epidermal nevus (ILVEN) is a variant of epidermal nevus that can be present at birth, but often presents in childhood. It is characterized by unilateral pruritic, erythematous, and hyperkeratotic papules that coalesce into plaques in a linear array (picture 8). ILVEN does not regress spontaneously but undergoes periods of exacerbation followed by improvement. (See "Epidermal nevus and epidermal nevus syndrome", section on 'Inflammatory linear verrucous epidermal nevus'.)
●Linear cutaneous lupus erythematosus – Linear cutaneous lupus erythematosus (LCLE) is a rare variant of cutaneous lupus occurring most often in children [42,43]. LCLE often presents on the face and does not resolve spontaneously. A skin biopsy is necessary to confirm the diagnosis. Patients with LCLE may have other mucocutaneous manifestations of lupus. (See "Overview of cutaneous lupus erythematosus".)
●Linear morphea – Linear morphea is a form of localized scleroderma that follows Blaschko's lines. It is often found on the face and extremities of children. It does not resolve spontaneously and can lead to permanent scarring. Linear morphea can be distinguished from lichen striatus by the presence of atrophy and sclerosis, although early lesions may be hard to distinguish (picture 9). The histopathology of late linear morphea has epidermal atrophy and dermal fibrosis. The histopathology of early linear morphea may have some overlapping features with lichen striatus [44]. Also, there have been few case reports of facial lichen striatus preceding linear morphea, and therefore, it is recommended that facial lichen striatus lesions be followed until resolution [44]. (See "Juvenile localized scleroderma".)
●Linear lichen planus – Linear lichen planus (LLP) is a rare variant of lichen planus most commonly seen in children (picture 10). It can be distinguished from lichen striatus by histopathologic examination and direct immunofluorescence (DIF). In LLP, cytoid bodies are typically seen at the dermoepidermal junction and DIF is positive for multiple immunoglobulins. Lichen planus of the nail tends to involve multiple nails and the entire nail plate (picture 11), whereas lichen striatus often only involves one nail and only the lateral or medial portion of the nail plate (picture 2) [45]. (See "Lichen planus".)
●Lichenoid chronic graft-versus-host disease – Lichenoid chronic graft-versus-host disease may present with a linear eruption along the lines of Blaschko [46,47]. It can be distinguished from lichen striatus by histopathology and history of bone marrow transplantation. (See "Cutaneous manifestations of graft-versus-host disease (GVHD)".)
●Linear psoriasis – Linear psoriasis is a rare variant of psoriasis. The presence of well-demarcated, erythematous papules or plaques with overlying micaceous scale differentiates psoriasis from lichen striatus. In uncertain cases, histology can clarify the diagnosis. Patients with linear psoriasis may also have other sequelae of psoriasis. (See "Psoriasis: Epidemiology, clinical manifestations, and diagnosis".)
●Linear porokeratosis – Linear porokeratosis is a rare variant of porokeratosis that typically presents during infancy or early childhood with single or multiple plaques with hyperkeratotic rims on the limbs or trunk (picture 12A-B) [48]. Histology reveals the characteristic cornoid lamellae (thin columns of tightly packed porokeratotic cells within a keratin-filled epidermal invagination (picture 13A-C)). (See "Porokeratosis", section on 'Linear porokeratosis'.)
●Linear Darier disease – Darier disease is a rare autosomal dominant genodermatosis that usually appears during the teenage years as skin-colored or yellow-brown keratotic papules on the face, chest, and back, and, less frequently, the flexural areas. Linear forms of Darier disease can be differentiated from lichen striatus by the typical histopathologic finding of acantholytic dyskeratosis [49]. (See "Darier disease".)
●Incontinentia pigmenti – Incontinentia pigmenti is a rare X-linked dominant genodermatosis that is usually lethal in males and presents in the neonatal period with linear papules and vesicles. Within weeks or months, the initial lesions progress to verrucous streaks (picture 14) and then progress to hypopigmented and finally hyperpigmented whorls along the Blaschko lines (picture 15). (See "Vesicular, pustular, and bullous lesions in the newborn and infant", section on 'Incontinentia pigmenti'.)
TREATMENT — Lichen striatus is a benign, self-limited condition that is often asymptomatic; therefore, treatment is often not necessary. Patients and their parents or caregivers should be reassured that the eruption will resolve spontaneously in several months without scarring, leaving a transient hypopigmentation. The hypopigmentation can last several years.
Low- to mid-potency topical corticosteroids may be used for the symptomatic treatment of pruritus, but they have no effect on the duration of the disease or postinflammatory dyspigmentation [6]. There are isolated reports of successful treatment of lichen striatus with topical calcineurin inhibitors [50-52]. Excimer laser has been used to treat the residual hypopigmentation of lichen striatus and has led to repigmentation in a small number of cases [53]. Similarly to the skin lesions, nail lichen striatus often resolves spontaneously, but the course can be prolonged. Treatment with intralesional triamcinolone injected into the medial and lateral proximal nail folds targeting the nail matrix has been described to hasten improvement [54].
SUMMARY AND RECOMMENDATIONS
●Lichen striatus is a benign, self-limited, inflammatory dermatitis that follows the lines of Blaschko. It predominantly affects young children and adolescents. (See 'Introduction' above and 'Epidemiology' above.)
●Lichen striatus typically presents as a single, unilateral band of red, pink, or skin-colored flat-topped papules (picture 1C). The most common locations are the extremities, followed by the trunk (picture 1D), buttocks, face (picture 1A-B), and nails (picture 2). Bilateral or multiple bands may also occur (picture 3). (See 'Clinical manifestations' above.)
●The diagnosis of lichen striatus is usually clinical. If the diagnosis is in question, a skin biopsy may be necessary for histopathologic confirmation. (See 'Diagnosis' above and 'Pathology' above.)
●Lichen striatus resolves spontaneously without treatment over several months, leaving a postinflammatory hypopigmentation. Topical corticosteroids can be used for the symptomatic treatment of pruritus. (See 'Treatment' above.)
