Lichen planus follicularis tumidus of the scalp: A rare histopathological diagnosis

Dear Editor,

We report a 41-year-old male patient who presented with an asymptomatic elevated skin lesion associated with hair loss over the right retro-auricular scalp and on the frontal scalp for 1 year and 6 months, respectively. On cutaneous examination, two well-defined, ∼3 × 4 cm, violaceous to hyperpigmented plaques with hair loss were present [Figure 1]. Examination of nail, mucosa, and other body areas revealed no abnormality. The hair pull test was negative. The patient denied any history of trauma, bullous lesions, use of any topical treatment, or hearing aid. Dermoscopy of the lesions demonstrated follicular plugging, perifollicular hyperpigmentation, and reticular Wickhams’ striae [Figure 2]. Based on clinical and dermoscopic examination, a differential diagnosis of lichen planopilaris and lichen simplex chronicus was considered. Routine laboratory investigations were within normal limits. Serology for Hepatitis B and Hepatitis C was negative, and the thyroid function test was normal. Histopathological examination of the 4 mm punch biopsy taken from the frontal scalp and stained with haematoxylin and eosin stain revealed epidermal changes like compact hyperkeratosis, hypergranulosis, and acanthosis. Multiple miliary cysts were present throughout the thickness of the dermis. Lichenoid interface, melanin incontinence, and hypergranulosis were present in each milia-like cyst. Compact keratin was seen in each milia-like cyst [Figure 3a-b]. Alcian blue stain for mucin was negative. The presence of milia-like cysts ruled out the initial provisional diagnosis of lichen planopilaris and lichen simplex chronicus. Based on the clinical, dermoscopic, and histopathological examination, lichen planus follicularis tumidus (LPFT) was confirmed. No lesions of typical lichen planus were present over any other cutaneous sites. We started the patient on capsule cyclosporine at a dose of 3 mg/kg/day in two divided doses with intralesional triamcinolone acetonide (10 mg/mL) every 21 days.

Close

Figure 1a:

A well-defined hyperpigmented to violaceous plaque with hair loss over the frontal scalp.

Export to PPT

Close

Figure 1b:

A well-defined hyperpigmented to violaceous plaque with hair loss over the right retroauricular area.

Export to PPT

Close

Figure 2:

Polarised trichoscopy (10x) demonstrating follicular plugs (black arrow), perifollicular hyperpigmentation (yellow arrow), and reticular Wickhams’ striae (red arrow).

Export to PPT

Close

Figure 3a:

Histopathology demonstrating compact hyperkeratosis (black arrow), miliary cysts (red arrow), and compact keratin in each cyst (black asterisk) (Haematoxylin & eosin, 40x).

Export to PPT

Close

Figure 3b:

Histopathology demonstrating lichenoid interface (white arrow) and melanin incontinence (yellow arrow) (Haematoxylin & eosin, 100x).

Export to PPT

LPFT is an extremely rare adnexotropic variant of lichen planus.¹ Belaich et al.,² described the first case of LPFT as a variant of lichen planus in 1977. The most common sites involved are the retroauricular areas.¹ A review of other reported cases from around the world has been mentioned in Table 1.

Histopathologically, LPFT is a variant of lichen planopilaris.⁴ It is called LPFT due to the presence of yellow milia-like cysts and comedones, giving a tumid appearance to the clinical morphology. Follicular mucinosis and Milia en plaque were considered as histopathological differential diagnoses. Follicular mucinosis was excluded due to the lack of mucin in the hair follicles. Milia en plaque doesn’t show apparent lichenoid infiltrate. LPFT can be differentiated from discoid lupus erythematosus clinically by the absence of central depigmented plaque with follicular plugging surrounded by a hyperpigmented rim, on trichoscopy by absence of yellow dots, thin red arborising vessels, and histopathologically by the absence of interface dermatitis accompanied by perivascular and periadnexal lymphoplasmacytic infiltrate. According to a report by Saggini et al,⁵ immuno-histochemistry (IHC) evaluations in a case of LPFT revealed a significant population of small CD8⁺ lymphocytes among the CD3⁺ cells, with generally preserved expression of pan-T-cell markers. LPFT is a disease with a chronic relapsing course and is very resistant to treatment.⁵ The commonly reported associations include hepatitis B, hepatitis C, Hashimotos thyroiditis, and immune checkpoint blockade agents.¹ Treatment with topical and systemic steroids and oral and topical retinoids has been attempted.⁶

In conclusion, LPFT is a rare clinico-pathological variant of lichen planus and may present with milia and comedones on an inflamed plaque. We are reporting this case because LPFT is a rare histopathological diagnosis with clinical and trichoscopic features common to other disorders.