An asymptomatic and otherwise healthy 2-year old Hispanic girl presented with a “rash” of 2 months duration on the dorsolateral aspect of her right wrist. She was accompanied by her mother, who reported that onset of the “rash” was sudden and was initially about 1 cm in length. The mother had been applying an ointment prescribed by the pediatrician for about a month, but the rash slowly expanded. The girl had a negative past medical history and a negative family history for dermatologic disorders; she had no allergies to medications and was not taking any at the time. No evidence of atopy was found, and there was no recent report of infection in the girl. On physical examination, there was a mildly erythematous plaque made up of coalescent papules and some scale localized on the dorsolateral aspect of the right wrist in a linear fashion, measuring 6 cm in length. There was absence of pruritus, vesicles and crusts. What is Your Diagnosis?
Diagnosis: Lichen Striatus
Lichen striatus (LS), first described by Francis Eugene Senear, MD, and Marcus Rayner Caro, MD, in 1941.1 is a rare and benign linear dermatosis that primarily affects children. It is clinically diagnosed on the basis of its appearance and characteristic developmental pattern following the lines of Blaschko. These skin lesions usually appear as a continuous or interrupted linear band of 1 cm to 3 mm pink, tan, or skin-colored lichenoid papules, which can be smooth, scaly, or flat-topped. Occasionally, a vesicular component is present. The band may range from a few millimeters to 1 mm to 2 cm wide and may extend from a few centimeters to the full length of an extremity. The lesions manifest most commonly on the extremities and less commonly on the trunk, face, and nails.2 It has been suggested that LS be renamed as “blaschkitis,” “blaschko dermatitis, or “Blaschko linear inflammatory skin eruption (BLAISE).”3
LS is primarily a disease of young children and adolescents aged 5 to 15 years.1,4,5 The mean age of onset is 4 years 5 months and median age of onset is 3 years.6 Although LS is uncommon in adults, the disease can occur in persons of any age.7 Some of the larger studies to date show a female predominance by 2:1 or 3:1.6,7,8
The classic and most common presentation of lichen striatus is pink or skin-colored, flat-topped papules, often uniting to form plaques and following the lines of Blaschko.6 The papules may be smooth or scaly. Lichen striatus usually appears acutely on a solitary extremity, the trunk or the face,1 and takes several days or weeks for maximum involvement.6 Studies in the past have not shown conclusive data to support preference of either upper or lower limbs. In rare cases, LS may be bilateral or occur in multiple parallel bands.1 Some authors have concluded that trunk or facial lesions always follow the developmental lines of Blaschko, invisible anatomic lines that trace the pathway of ectodermal cell migration; which were first described in 1901 by Alfred Blaschko.6 Lichen striatus is usually asymptomatic but can be accompanied by pruritus, which may be due to an associated atopy rather than LS itself.6,7 Less commonly reported presentations are either hypopigmented macules and/or papules or nail involvement.6 Nail lichen striatus is the rarest presentation and typically features longitudinal ridging and splitting along the medial or lateral aspect of a single nail.9 There are fewer than 30 reported cases involving the nails worldwide, according to a report in 2002 by Kavak and Kutluay.2 Nail involvement may be the only presentation, or it may be accompanied by cutaneous manifestations. Nail changes can include onycholysis, thinning or thickening of the nail plate, nail pitting, and over-curvature of the nail plate.2
The most widely accepted etiology is the combination of genetic predisposition with environmental stimuli.2 However, many etiologic or predisposing factors have been suggested as single causes of lichen striatus. One group reported that 85% of patients with lichen striatus have a family history of atopic dermatitis, asthma or allergic rhinitis, suggesting that atopy is the predisposing factor. However, another report disputes this claim, stating that the incidence of atopy is no greater than that of the general population.2 Others believe that LS may be associated with an autoimmune response. A case of lichen striatus during pregnancy led to the speculation that the pregnancy triggered an autoimmune response and subsequent eruption.14 In 1995, evaluation of the immunohistochemical aspects of 10 cases had demonstrated a CD8+ T-cell mediated response to keratinocytes in the epidermis.10 Somatic mutation of a keratinocytic clone may have induced autoimmunity. In support of this theory, it is widely believed that Blaschko lines are clonal outgrowths of cutaneous embryologic cells. In 2000, Hauber et al proposed that lichen striatus begins as a post-zygotic mutation that leads to a congenital presence of an abnormal clone of skin cells. Then, an acquired event (eg, viral infection) may enable these cells to express a new antigen, resulting in the phenotypic skin changes.11 The association of LS with autoimmunity is a possible consideration because of the occasional occurrence of autoimmune diseases such as vitiligo and lupus erythematosus in a Blaschko line distribution.8 An environmental (infectious or traumatic) etiology has also been suggested. Familial cases, outbreaks among unrelated children in a shared living environment, and a possible seasonal variation suggest an environmental agent, such as a virus. Lichen striatus has been reported to occur shortly following immunization with BCG and hepatitis B vaccination and after varicella infection.2 However, results of testing have not conclusively proven a viral association. Spontaneous involution, however, suggests the notion of a viral etiology.12 In the Acta Dermatovenerologica Alpina, Panonica, et Adriatica, a 2006 case report by Dragos, Mervic and Zgavec revealed a 15-month-old girl who developed lichen striatus on the trunk and single extremity after receiving the combined vaccine against measles, mumps and rubella.3
It is rarely necessary to perform a skin biopsy, but if done, it can help differentiate LS from other linear dermatoses such as linear lichen planus. For example, stains for immunoglobulin M, immunoglobulin G, and complement C3 are positive in lichen planus and negative in lichen striatus.2 Similar to LS, lichen nitidus is often asymptomatic; however, lesions are typically 1 mm to 2 mm skin-toned papules that may be umbilicated or scaly on physical examination. Unique to lichen nitidus are groups of lymphocytic infiltrates and elongation of rete ridges directly adjacent to each infiltrate. Inflammatory linear verrucous epidermal nevus (ILVEN) clinically presents as pruritic, erythematous and verrucous papules that typically do not spontaneously regress as in lichen striatus. The histology of ILVEN usually shows a perivascular infiltrate that is more superficial and focally located in the epidermis. Refer to above table for a complete list of differential diagnoses.
The histopathologic results vary depending on the stage of evolution. One of the remarkable features of lichen striatus, unlike lichen planus, is a dense, usually perivascular, lympho-histiocytic infiltrate that extends deep into the dermis and surrounds eccrine sweat glands and hair follicles.2,8 Immunohistochemistry has demonstrated that most of the lymphocytes in the upper dermis are CD7-positive, while most of the lymphocytes in the epidermis are CD8-positive.4 Based on one study, consistent histologic features were hyperkeratosis, parakeratosis, few necrotic keratinocytes in the epidermis, and mild spongiosis with exocytosis of lymphocytes.4 The initial event may be intercellular edema causing loss of contact between keratinocytes. This leads to tonofilament aggregation at the cell membrane and subsequent vacuolization within the cytoplasm of these keratinocytes. Finally, vacuolization leads to cytolysis and formation of the dyskeratotic cell, which may closely resemble the corps ronds of Darier’s disease.13 In later stages, there is disruption of the basal layer with residual cavities.
Lichen striatus is self-limiting and spontaneously regresses within 3 to 12 months after onset, and therefore, medical treatment is not necessary. The patient and family should be reassured of the benign nature of LS. If present, nail involvement also resolves spontaneously without deformity within 30 months.14 Corticosteroids do not seem to shorten the duration of the inflammatory stage or influence the duration of the post inflammatory hypopigmentation.6 However, emollients and mild or medium-strength topical corticosteroids have been used to reduce associated dryness and pruritus.6,7 There are some patients with relapsing, disseminated, or nonresponsive, and more pruritic LS. Recent studies were done to find topical alternatives for such cases. Immunomodulators such as 0.03% tacrolimus (Protopic) and 1% pimecrolimus (Elidel) ointments were shown to be beneficial, but larger studies are needed to confirm their efficacy and safety.15 In addition, a small study showed that early treatment with tacrolimus has the potential to reduce hypochromatic sequelae in patients with dark skin.9 Our patient was treated with 0.005% fluticasone propionate ointment applied twice daily. On follow-up 2 weeks later, the patient’s linear lesion was found to have regressed in size without any complications. The flat-topped, pink papules appeared less discrete and palpable than on presentation.
The prognosis for lichen striatus is excellent. For most patients, the lesions usually regress spontaneously within a range of 2 month to 10 years (mean of 6 months; median of 5 months).6 There have been rare cases in which lesions are present for greater than 10 years.6 Relapses have been observed in rare cases. Post inflammatory hyperpigmentation and hypopigmentation may occur and last for several months to years after the disease resolves.2 Studies in the past have been small in scale and often show conflicting epidemiologic data and multiple etiologic factors. Why does lichen striatus mostly affect the pediatric population? Even though it is widely accepted as benign, are there any long-term sequelae? Larger scale studies are needed to determine its exact pathogenesis and triggering factors. Elaine Phuah is a third-year medical student at Kansas University of Medicine and Biosciences in Kansas City, MO. Dr. Schiffman is the senior resident of dermatology at St. John’s Episcopal Hospital in Far Rockaway, NY. Dr. Khachemoune, the Section Editor of Derm Dx, is with Department of Dermatology, State University of New York, Brooklyn, NY. Disclosure: The authors have no conflict of interest with any material presented in this month’s column.