Lichen striatus: clinical features and follow-up in 12 patients

ARTICLE

Lichen striatus (LS) is an uncommon linear papular eruption which mostly occurs in children but may also be seen in adults. It usually consists of asymptomatic inflammatory papules in linear arrangement located on either of the extremities. The lesions are self-limiting and have been reported to involute within one year in most cases [1].

In the following, we present the clinical and histological features of 12 consecutive cases of LS diagnosed in our department between 1996 and 1999 and compare them with published series. Although LS was described in the late 19th century it was not until 1941 that it was delineated as a distinctive clinical and pathological entity by Senear and Caro [2]. To avoid overvaluing unusual cases, we included only series with at least 2 patients in our review of the literature. To make sure to separate LS from its most important differential diagnosis, inflammatory linear verrucous epidermal nevus (ILVEN), delineated in 1971 [3, 4], we further included literature data published only after that year.

Report of Cases

Patients: Twelve cases of lichen striatus (LS) diagnosed in our department between 1996 and 1999 were reviewed. In all cases skin biopsies were taken after informed consent in order to support the clinical diagnosis and to exclude other acquired linear skin eruptions. The male gender predominated by 9:3. Age at diagnosis varied from 6 months to 48 years, with a median age of 5 years. Ten out of the 12 patients were children aged 6 months to 12 years, and only 2 patients were adults aged 25 and 48 years, respectively. As shown in Figure 1, the mean duration of the inflammatory eruption was 12 months, ranging from 4 months to 4 years. A relationship between the patient's age at time of onset and the duration of LS was not evident.

Clinical features: Without exception, the skin lesions followed the lines of Blaschko and consisted of only one streak or whorl of reddish papules with mostly moderate scaling (Fig. 1). Most lesions were said to have spread in a centrifugal way. They were located on the lower limbs in 6 of the 12 patients, on the upper limbs in 4, and on the trunk in the remaining 2 patients. Two of the patients showed nail involvement in terms of onychodystrophy and longitudinal ridging in distal extension to the skin lesions (Fig. 2a). In one case the nail lesion appeared shortly after, in the other case simultaneously with the skin eruption (Fig. 2b). However, the nail dystrophy disappeared only about 4 months after the regression of the cutaneous papules.

Only 2 out of the 12 patients noted pruritus. In the other patients the lesions were asymptomatic. Postinflammatory hypopigmentation was noted in 5 cases, and postinflammatory hyperpigmentation in 4 patients whereas the remaining 3 patients showed no residual effects at all. A correlation between the kind of postinflammatory pigmentation and the season of the year was not evident. Most of the patients had skin type 2 according to Fitzpatrick.

A positive personal history of atopic disorders including atopic dermatitis and allergic rhinoconjunctivitis could be obtained from 7 of the 12 patients.

Histological features: Biopsy specimens of all 12 patients were reviewed and the histological features were consistent with the diagnosis of LS. In all cases there was a lichenoid interface dermatitis with a superficial and deep inflammatory infiltrate mostly composed of lymphocytes. The infiltrate aligned along the follicles and eccrine ducts (Fig. 3). In 2 cases the deep inflammatory infiltrate was only sparse. Various degrees of acanthosis, focal spongiosis, and slight parakeratosis were apparent. Necrotic keratinocytes were seen at the dermo-epidermal junction and scattered within the epidermis.

Discussion

LS is an inflammatory linear eruptive disease which, as the present series confirms, mainly affects children but may also occur in adults. Age at onset varies considerably, in our patients from 6 months to 48 years, in other series from 6 months to 37 years [5, 6], and in one study even up to 70 years, with the majority of patients being pre-school aged [7]. In contrast to literature data showing a clear preference for the female gender [6, 8] or an equal sex distribution [5, 18], 9 of our 12 patients were male.

LS is a self-limiting dermatosis with a reported duration of 4 weeks to 6 years until complete remission [5, 7]. In the present series, lesions lasted for 4 months to 4 years with a median duration of 12 months. Important to note, a linear inflammatory disease lasting over one year may thus still be consistent with the diagnosis of LS. Patient's age at time of onset and duration of the lesions do not seem to correlate. None of our patients showed a relapse which is consistent with most other observations. However, there are a few reports of recurrences in an identical distribution [5, 8].

LS almost always occurs sporadically although there are 3 reports on simultaneous occurrences in 2 related siblings [1, 8, 9] and one in 2 nonrelated siblings [10]. In our series, no other family member or contact person of the patients had a history of the condition. Lesions followed the lines of Blaschko in all 12 patients. Although this pattern of distribution has been doubted by some authors [2, 11], LS is listed among acquired linear eruptive diseases following Blaschko's lines in reviews of Jackson [12] and Bolognia [13]. Taïeb et al. even proposed BLAISE for Blaschko linear acquired inflammatory skin eruption as a new acronym for LS [5]. In our series, all patients showed solitary unilateral streaks which matches well with the observations of other authors. In a few instances, LS was reported to show a diffuse and bilateral distribution [14, 15]. Lesions in our patients were confined to the lower limbs in 6 patients, to the upper limbs in 4 and to the trunk in 2 patients. Kennedy and Rogers also report involvement of the legs to be 1.7 times more often than of the arms [8]. In contrast, the upper limbs were markedly more often involved in other series [5, 7].

Two of our patients showed nail involvement in terms of onychodystrophy and longitudinal ridging. In one case the nail lesion appeared shortly after, in the other case simultaneously with the skin lesion. Both occurred in the distal extension of the involved line and resolved completely some months after the skin lesions. According to Tosti et al., nail LS is not always associated with skin lesions or may precede the onset of cutaneous LS by up to 18 months [16]. Nail biopsies taken from patients with LS limited to the nails showed lichen planus-like changes of the nail matrix [16]. However, in contrast to nail matrix lichen planus, which causes permanent damage of the nail, nail matrix LS regresses spontaneously [16]. In our 2 patients with nail lesions we refrained from taking nail biopsies since the diagnosis was evident from the clinical and histological features of the skin lesions.

In our patients, skin lesions healed with postinflammatory hypopigmentation in 5 and with hyperpigmentation in 4 cases. Hypopigmentation has been reported considerably more often in other series [5, 7, 8]. The kind of pigment disturbance probably depends on the skin complexion of the patient, with postinflammatory hypopigmentation occurring more often in darker-skinned people. A correlation between the kind of postinflammatory pigmentation and the season of the year could not be found in the present study.

LS is an asymptomatic eruptive disease with pruritus being the only and rarely occurring symptom [5, 7, 18]. Only 2 of our 12 patients complained about slight pruritus which matches quite well with other series reported in the literature (Table I).

The pathogenesis of LS is still obscure. Having in mind Happle's interpretation of the lines of Blaschko as a result of clonal outgrowth of cutaneous embryonic cells [17], Taïeb et al. proposed the congenital presence of an abnormal skin clone due to a postzygotic mutation as a possible explanation for LS [5]. The cells bearing the mutation would only become visible if a sudden event were to cause this aberrant clone to express a novel membrane antigen, a viral infection being the most likely candidate. In our retrospective series, patients or their parents, respectively, were not aware of a viral infection before or at the time of onset of the skin lesions. However, mild or inapparent infections cannot be excluded.

Intrigued by the findings of DiLernia et al. [18] and Toda et al. [6] about a possible relationship between LS and atopy, we looked for a personal history of atopic disorders in our patients. Seven out of our 12 patients suffered or had suffered from atopic dermatitis and/or allergic rhinoconjunctivitis, whereas a "naevus atopicus" as described by Taïeb could be excluded by clinical and histological aspect [19]. As shown in Table I, others have also observed a higher prevalence of atopic disorders among LS patients [5, 18]. An atopic diathesis may therefore predispose to LS or, if the theory mentioned above holds true, to an infection triggering the manifestation of LS.

LS is a benign dermatosis which needs no treatment since it is self-limiting and, in most cases, asymptomatic. Skin biopsies serve to differentiate it histologically from other linear dermatoses [20, 21] and to reassure patients and their parents about the benign course of the condition.

There are a number of differential diagnoses of linear papular eruptions to consider. Besides linear psoriasis, linear Darier's disease, linear lichen planus and other linear nevi, inflammatory linear verrucous epidermal nevus (ILVEN) is the most important one. ILVEN is always pruritic which, however, is not a reliable differential criterion to LS. In contrast to LS, ILVEN does not regress spontaneously but can undergo periods of exacerbation and improvement. It may be present at birth but, in most cases, appears during infancy and childhood [3]. Histologically, ILVEN can be distinguished from LS by an acanthosis with alternating orthokeratosis and parakeratosis and a mild to moderate superficial lymphocytic infiltrate. If LS occurs in advanced age the diagnosis of adult blaschkitis first described by Grosshans and Marot in 1990 has to be taken into account [22]. As adult blaschkitis and LS show many parallels some authors believe that LS is the equivalent of adult blaschkitis in childhood [22]. However, adult blaschkitis, in contrast to LS, exclusively affects adults, never heals with postinflammatory hypo- or hyperpigmentation and, most importantly, lesions of adult blaschkitis show a shorter duration than LS lesions and are usually followed by several relapses [22, 24-26]. Histological examination of the few reported cases of adult blaschkitis shows a spongiotic dermatitis [24, 26].

CONCLUSION

In conclusion we can confirm from our series that LS is an inflammatory linear dermatosis which may affect both skin and nails and which occurs more often but not exclusively in children. It seems to arise more often in individuals with an atopic diathesis. Occasional duration of the eruption up to 4 years until complete remission shows that a linear inflammatory eruption lasting over one year can still be consistent with the diagnosis of LS. As shown, nail lesions are also completely reversible.

Article accepted on 19/07/00

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