BACKGROUND: Lichen striatus is a benign dermatosis that affects mainly children. This condition mimics many other dermatoses.
OBJECTIVE: The purpose of this article is to familiarize pediatricians with the clinical manifestations of lichen striatus to avoid misdiagnosis, unnecessary investigations, unnecessary referrals, and mismanagement of lichen striatus.
METHODS: A search was conducted in June 2023 in PubMed Clinical Queries using the key term \"Lichen striatus\". The search strategy included all observational studies, clinical trials, and reviews published within the past ten years. Only papers published in the English literature were included in this review. The information retrieved from the above search was used in the compilation of this article.
RESULTS: Lichen striatus is a benign self-limited T-cell mediated dermatosis characterized by a linear inflammatory papular eruption seen primarily in children. The onset is usually sudden with minimal or absent symptomatology. The eruption in typical lichen striatus consists of discrete, skin- colored, pink, erythematous, or violaceous, flat-topped, slightly elevated, smooth or scaly papules that coalesce to form a dull red, potentially scaly, interrupted or continuous band over days to weeks. Although any part of the body may be involved, the extremities are the sites of predilection. Typically, the rash is solitary, unilateral, and follows Blaschko lines. In dark-skinned individuals, the skin lesions may be hypopigmented at onset. Nails may be affected alone or, more commonly, along with the skin lesions of lichen striatus. The differential diagnoses of lichen striatus are many and the salient features of other conditions are highlighted in the text.
CONCLUSIONS: Lichen striatus is a self-limited condition that often resolves within one year without residual scarring but may have transient post-inflammatory hypopigmentation or hyperpigmentation. As such, treatment may not be necessary. For patients who desire treatment for cosmesis or for the symptomatic treatment of pruritus, a low- to mid-potency topical corticosteroid or a topical immunomodulator can be used. A fading cream can be used for post-inflammatory hyperpigmentation.

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There have been many reports of congenital and acquired dermatoses that trail Blaschko lines. Lichen striatus is representative of an acquired cutaneous linear inflammatory dermatosis running along the lines of Blaschko, characterized histopathologically by the predominance of lichenoid infiltration. Adult blaschkitis, however, is considered under the same disease spectrum as lichen striatus and is characterized by a spongiotic reaction pattern. Few differences have been recognized between lichen striatus and adult blaschkitis such as age of onset, triggers, distribution, histopathology, and response to treatment. A case of male patient with adult blaschkitis presenting as unilateral asymptomatic erythematous edematous papules, papulovesicles, and plaques over Blaschko\'s lines, in which skin biopsy revealed coexistent pathological features of lichen striatus and adult blaschkitis along with blood eosinophilia, has been presented here. This may add to the cumulative evidence on the pathogenesis of adult blaschkitis as an allergic reaction to an unknown inciting allergen. Evidence to consider adult blaschkitis as part of the lichen striatus spectrum is growing. Triggers for such skin reactions remain diverse. This case presentation suggests that adult blaschkitis could be triggered by an allergic response evidenced by the blood eosinophilia when other causes of eosinophilia are excluded.

Linear hyperpigmentation is an unusual anatomical configuration in clinical dermatology. Owing to its rarity, consensus on the most effective method of classification is lacking. While linear hyperpigmentation generally follows Blaschko\'s lines, this is not universal. Clinical findings such as adherence to Blaschko\'s lines, associated morphological findings (including other cutaneous lesions), and systemic manifestations can be used to further characterize and diagnose variants of the disorder. Early detection of any underlying disease is vital, especially in cases with effective management, because the disorder may make it difficult to manage hyperpigmentation. Herein, we introduce a logical clinical diagnostic approach that represents a useful tool for dermatologists to efficiently evaluate patients presenting with linear hyperpigmentation. A simplified systematic and evidence-based approach is useful for this clinical condition owing to the heterogeneous causes and lack of specific diagnostic tools.

Cutaneous conditions can follow Blaschko\'s lines on the skin, which are thought to reflect patterns of cell migration and clonal expansion during embryonic development of the epidermis. These diseases are hypothesized to be caused by genetic mosaicism resulting from processes such as lyonization or somatic postzygotic mutation. Lichen striatus and blaschkitis are two such acquired inflammatory skin disorders that are distinguished in the literature by age of onset, location, and histopathological features. Lichen striatus is typically observed on the extremities of children and is characterized by lichenoid papules that appear in a linear distribution along Blaschko\'s lines. Microscopic examination typically shows spongiosis, as well as lichenoid and periadnexal inflammation. Blaschkitis more commonly occurs in adults and frequently involves the truncal areas, including the chest and abdomen. Microscopic examination typically shows spongiotic dermatitis. We describe a young man with a linear eruption extending from the flexor aspect of his right wrist to his central chest, which has features of both lichen striatus and blaschkitis. Both lichen striatus and blaschkitis are self-limited diseases that may resolve within months. It has been suggested that lichen striatus and blaschkitis are not separate entities, but rather the two endpoints within the spectrum of blaschkolinear acquired inflammatory skin eruption (BLAISE). The overlapping features of lichen striatus and blaschkitis in our patient demonstrate the spectrum of clinical and pathologic features in patients with BLAISE.

BACKGROUND: Herein, we report a case of systemic cutaneous T-cell lymphoma refractory to standard therapy, the course of which resulted in haplo-identical bone marrow grafting.
METHODS: A 53-year-old woman consulted for facial erythema with infiltration, keratotic lesions on the trunk, and adenopathies measuring around 1cm on the axilla and inguinal folds. A diagnosis was made of Sézary syndrome (SS), a leukaemic form of epidermotropic cutaneous T-cell lymphoma. After three years of treatment with methotrexate, the patient developed transformed SS with visceral involvement. Given the high risk of relapse and the absence of an HLA-compatible donor, haploidentical bone marrow grafting was performed. The patient was still in complete remission two and a half years later. The disease course was nevertheless marked by the emergence one year after grafting of a Blaschko-distributed lichenoid eruption having histological features consistent with chronic graft-versus-host disease (GVHD); treatment with topical betamethasone proved efficacious.
CONCLUSIONS: To our knowledge, this is the first reported case of haploidentical grafting for systemic and transformed cutaneous T-cell lymphoma. This approach could henceforth represent a therapeutic option for patients requiring an allograft in the absence of compatible donors. The Blaschko-distributed lichenoid lesions attributed to chronic GVHD could be the result of reduced immune tolerance to abnormal embryological clones leading to a T-lymphocyte-mediated inflammatory reaction.

Lichen nitidus is a rare, chronic dermatosis which occurs more often in children than in adults. It presents with tiny, monomorphous, lichenoid, mostly asymptomatic papules in regional or disseminated distribution which show a pathognomonic histological pattern. The pathogenesis is unclear; however, immunologic phenomena and genetic factors are under discussion. In rare cases, an association with other dermatoses and systemic diseases has been described. Moreover, medical treatments have been incriminated as triggers. Considering the self-limited course in mostly young patients, treatment must be thoroughly weighed. Possible therapeutic options include topical corticosteroids and calcineurin inhibitors as well as oral antihistamines, corticosteroids and narrow-band ultraviolet B phototherapy. Lichen striatus is an acquired, usually asymptomatic dermatosis occurring mostly in preschool children. The characteristic feature is the arrangement of small, flat, light red- to skin-colored papules along the lines of Blaschko. Therefore, a postzygotic mutation of epidermal progenitor cells induced to express new surface antigens by trigger factors as infections, vaccinations or trauma with consecutive immune reaction is assumed. Nail involvement of the affected limb can rarely occur. Lichen striatus usually heals without scarring within several months, so that therapies with severe side effects are obsolete. Mild topical corticosteroids or calcineurin inhibitors may be used, especially if patients exceptionally suffer from pruritus. A postinflammatory hypopigmentation can persist for months to years.

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Linear dermatoses are fascinating entities that likely reflect embryologically derived cutaneous mosaicism, even when they occur after childhood. Adult blaschkitis is a rare, relapsing inflammatory dermatitis that most often presents in middle age. It presents clinically as a pruritic eruption of linear papules, vesicles and plaques, and is most commonly found to have features of spongiotic dermatitis on pathology. However, the clinical and histopathologic presentation of lichen striatus in adults may be similar to those of adult blaschkitis. A case in which \'blaschkitis\' was suspected clinically is presented, in which the biopsy showed non-characteristic microscopic features resembling erythema multiforme--a finding rarely reported in the literature to date. We present this case and a brief review of the most commonly acquired linear eruptions following Blaschko\'s lines with the goal of expanding the histopathologic findings that may be encountered in adult blaschkitis. Moreover, the clinical and histopathologic overlap between the entities of blaschkitis and lichen striatus is explored, acknowledging that these entities may exist on a clinicopathologic spectrum. In the diagnosis of linear eruptions, clinicopathologic correlation is important for arriving at an accurate final diagnosis.

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