Dermoscopic Signs in the Diagnosis of Lichen Planus Follicularis Tumidus.

Sir,

We read with interest the manuscript by Vaishali H et al., in which they described a case of lichen planus follicularis tumidus involving bilateral retroauricular areas.[1] We had experience of a strikingly similar case, and we want to make some contributions.

Lichen planus follicularis tumidus (LPFT) represents a rare subtype of lichen planus (LP). Fewer than 20 cases have been reported in the medical literature. Clinically, it manifests as tumid violaceous plaques with keratin-filled mila-like cysts and comedones most commonly affecting the retroauricular area. Here we report the clinical, dermoscopic, and histopathological features of an additional case of LPFT. A dermoscopic–histopathological correlation was performed.

A 58-year-old male with type 2 diabetes presented with bilateral mildly itchy plaques in both retroauricular areas, present for at least 4 months. He reported a history of vigorous and repeated rubbing on the retroauricular area during a steam bath few days before the skin lesions appeared. On examination, well-delimited violaceous and infiltrated plaques with multiple whitish/yellowish cysts were noted behind both ears [Figure 1]. Rest of the skin, mucous membrane, hair, and nails were spared. Dermoscopically, the lesions exhibited perifollicular pigmentation, follicular plugs, multiple rosettes and Wickham striae [Figure 2]. Pathological examination revealed a slightly acanthotic epidermis with wedge shaped hypergranulosis. The upper dermis showed a dilated follicular infundibula filled with orthokeratotic keratinous lamellae, surrounded by a band-like lymphocytic infiltrate [Figure 3]. A few individually eosinophilic colloid bodies and pigmentary incontinence were also noted. The diagnosis of LPFT was made. Routine laboratory tests were either negative or normal, including screening for hepatitis B and C. We started a treatment with high potency topical corticosteroids and our patient was adviced to ovoid vigorous scratching.

Figure 1

Bilateral, well-delimited violaceous and tumid plaques with multiple whitish/yellowish cysts in both retroauricular areas (a_Right side; b_Left side).

Figure 2

Dermoscopy showing perifollicular pigmentation (Blue stars), follicular plugs (red squares), Wickham striae (yellow arrows), and small rosettes within large follicular openings (black circles). Polarized dermoscope with x10 magnification (Dermlite 4, 3GEN Inc, San Juan Capistrano, CA, USA).

Figure 3

(a)Dilated follicular infundibula (blue arrows) filled with orthokeratotic keratinous lamellae (yellow stars) (haematoxylin and eosin, X40). (b) Wedge shaped hypergranulosis (red stars) and a subjacent lymphocytic infiltrate (green stars) (haematoxylin and eosin, X200).

LPFT is an extremely rare variant of LP that most commonly affects the retroauricular area, although the cheeks and scalp may also be affected. It has been reported in association with other diseases such as hepatitis B and C, Hashimoto's thyroiditis and checkpoint blockade agents.[12]

In recent years, dermoscopy has been used as a diagnostic method in the investigation of inflammatory skin disorders. Wickham's striae detected in our case is a highly specific feature of LP and corresponds to the wedge shaped hyper granulosis on histopathology.[3] Pigment patterns correspond histologically to dermal melanophages and pigment incontinence. It may display different features according to the disease stage including 'diffuse peppering' pattern, “reticular” pattern and “perifollicular/annular” pattern seen in our case.[4] White rosettes are shiny white structures due to the optical effect between polarized light and follicular structures.[5] In our case, rosettes are related to intrafollicular concentric keratin.

Dermoscopic features of LPFT may provide helpful clues to the clinical diagnosis. Indeed, LPFT based on dermoscopic features can be easily differentiated from other differential diagnosis such as milia en plaque and follicular mycosis fungoides. The main dermoscopic features of milia en plaque are multiple milia cysts and comedo-like openings with branching vessels around.[6] In a published report of a pilot study of primary cutaneous lymphomas, perifollicular accentuation was identified in all follicular mycosis fungoides cases. It surrounded comedo-like openings in 60% of cases. This pattern can be contrasted to LPFT, which demonstrates perifollicular pigmentation related to the pigment incontinence.[7]

To the best of our knowledge, this is the first case report focusing on the dermoscopic features of LPFT.

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Nil.

Conflicts of interest

There are no conflicts of interest.