The term Wickham striae (WS) was coined by Louis Frédéric Wickham in the year 1895 and corresponds to fine white or gray lines or dots seen on the top of the papular rash and oral mucosal lesions of Lichen planus (LP),[1] also called as Lichen Ruber Planus.
Pathogenesis of Wickham Striae
Various pathological changes have been cited for formation of WS. The first theory cited by Darier et al. in the literature attributes the appearance of the WS to increase in the granular cell layer in the epidermis.[2] Summerly et al. gave the explanation of focal increase in the epidermal activity for the formation of striae.[3] A third pathological factor suggested by Ryan for formation of WS is lack of dermal vessels in the area which acts as a contributing factor.[4] The histological confirmation of the WS can be done by India ink staining in which the ink is retained on the stratum corneum.
Clinical Appearance of Wickham Striae
WS are seen as fine, white or grey lines on top of purple papular skin lesions of LP. Wickham, while originally describing them, noticed that these striae did not correspond to the scale on the surface of the papule as the striae were present on the non-scaly lesions too.Similarly, it was observed that WS were noticeable on the lesions on which the scale had been removed.[2] It has however not been described in literature that at which stage of evolution of LP, the WS first appear. WS are noticeable in the mouth lesions also. In oral cavity, the WS appear in tree-like configurations or in the form of a lacy network, usually located bilaterally and are seen with greater frequency on the buccal mucosa. These lesions can also be observed on the lateral margin of the tongue, gingiva, and lips.[5]WS are of special significance in the diagnosis of erosive form of oral LP, as this form may undergo malignant transformation.
Identification of Wickham Striae
On skin, it is easier to spot WS if a thin layer of oil is applied to the surface of the top of the papular lesions. The handheld dermatoscope (Delta 10: Heine Optotechnik, Munich, Germany) with a fixed magnification of 10 helps in the clinical confirmation of WS. It discretely shows the reticular whitish pattern of striae along with capillaries surrounding the striae as radial, horizontally oriented red lines or red dots.[6] The recognition of WS by this technique has especially been found useful when psoriasis lesions coexist with LP. Since both the diseases present with superficial scaly papular, plaque type lesions, for beginners it can be confusing. In such cases, presence of WS is considered to be a pathognomonic sign of LP. Dermoscopy is a well-recognized tool for identification of WS by Indian authors also.[7]
Wickham Striae in Pigmented Skin
WS are much more difficult to see and many times may not be visible at all in pigmented skin/skin of color. Also, the clinical picture of LP may differ from the classical one due to variations in morphology and configuration, or modifications of clinical features depending on the site of involvement. WS may not be clinically appreciated on lesions of LP when the patient has been previously taking treatment such as application of topical steroids or salicylic acid.
Differential Diagnosis
WS in oral LP may be simulated by atrophy and differentials include leukoplakia, frictional keratosis and oral lichenoid eruptions. Occasional lesions of LP in mouth are primarily erythematous, with very few white streaks, and these must be distinguished by biopsy from erythroplakia and erythroleukoplakia.[89]WS in cutaneous lesions of LP may be mimicked by scaly lesions in the following skin diseases:[10]skin lesions due to drug-induced photosensitivity (hydrochlorothiazide, hydroxychloroquine, and captopril)psoriasis (plaque type/guttate)discoid lupus erythematosuslichen nitiduspityriasis roseasecondary syphilisgraft versus host diseasetinea corporis
Conclusion
WS is an important diagnostic sign of LP and should always be looked for when confused or lesions coexist with similar scaly dermatosis.