An Atypical Presentation of Lichen Nitidus: Blaschkolinear Pattern Masquerading as Lichen Striatus

Dear Editor, Lichen nitidus (LN) is an uncommon papulosquamous dermatosis with an unknown etiology and pathogenesis characterized by multiple, 1–2 mm, flesh-colored, shiny, dome-shaped papules. Although asymptomatic, it may occasionally be associated with pruritus. It usually appears with limited involvement and sometimes becomes generalized. Lichen striatus (LS) is a benign, self-limiting, inflammatory skin disease that follows Blaschko’s lines. We report a LS-like blaschkolinear presentation of LN in an adolescent girl. An 11-year-old girl child presented with an asymptomatic whitish lesion over the left leg for 5 years. She had no complaints of itching. On elaborating history, there was a gradual increase in size over the last 1 year. However, the patient did not seek any treatment earlier. On examination, the patient had hypopigmented macules and patches in blaschkoid pattern over the left leg extending from the buttock to the ankle with mild scaling [Figure 1a]. There were hypopigmented to erythematous papules in similar distribution extending from ankle to the dorsal aspect of the great toe [Figure 1b]. Hair, nail, and mucosa were not involved. We considered the differential diagnosis of LS. To our surprise, dermoscopy (DinoLite 2.0 AM4113ZT polarized mode) showed circular hypopigmented area with central brown shadow [Figure 2a and b from the leg and foot, respectively]. This raised the suspicion of LN.Figure 1: (a) Multiple hypopigmented macules coalescing to form a patch in blashkolinear distribution on the posterolateral aspect of the left leg, (b) multiple hypopigmented to erythematous papules with scaling on the dorsum of the left ankle to great toeFigure 2: (a) Dermoscopy from the posteriorlateral aspect of the left leg showing hypopigmented circular area with central brown shadows (20, DinoLite 2.0-AM4113ZT, Polarized mode), (b) dermoscopy from dorsum of the left foot showing hypopigmented circular area with central brown shadows (×20, DinoLite 2.0-AM4113ZT, Polarized mode)Histopathology from a hypopigmented patch over the left posterolateral aspect of the leg revealed a well-circumscribed granulomatous infiltrate of lymphocytes, macrophages, and epithelioid histiocytes in the papillary dermis bordered by extension of elongated epidermal rete ridges giving characteristic “claw clutching the ball appearance” [Figure 3a-c]. There was epidermal thinning with hydropic degeneration of basal keratinocytes. Immunohistochemistry (IHC) was positive for CD68 staining [Figure 4a and b]. This confirmed the diagnosis of LN.Figure 3: (a) Histopathology from hypopigmented patch over posterolateral aspect of left leg showing well circumscribed granuloma composed of lymphohistiocytes and macrophages bordered by elongated epidermal rete ridges giving “claw clutching the ball appearance” (H and E stain, ×100), (b) Histopathology showing lymphohistiocytic infiltrate with prominent vacuolar interface (H and E stain, ×200), (c) Histopathology showing mixed infiltrate of lymphocytes and epitheloid histiocytes (H and E stain, ×400)Figure 4: (a and b) Immunohistochemistry with CD68 showing granular and cytoplasmic staining pattern of epitheloid histiocytes (CD68 staining, ×40 and × 400, respectively)She was prescribed topical clobetasol propionate 0.05% twice a day for 3 months. She reported mild improvement and kept under observation now. LN is a chronic inflammatory lichenoid dermatosis, more commonly seen in childhood or early adulthood. The sites commonly involved are the upper extremities, trunk, buttocks, and genitalia, with occasional involvement of nails and palms, and soles. LN usually presents as shiny, dome-shaped papules. Clinical variants of LN are confluent, vesicular, hemorrhagic, palmoplantar, follicular, perforating, linear, and generalized. There have been no reported cases of LS like LN, i.e., hypopigmented mild scaly macules in blaschkolinear distribution similar to our case. The dermoscopy of LN shows hypopigmentation, central brown shadow, linear vessels, accentuation of the surrounding reticulate pigment network, and diffuse erythema as the most common findings. Hypopigmented circles corresponded to acanthotic epidermis; central depression and brown shadows correlate with the focal dense ball-like infiltrate.[1] In contrast the dermoscopy of LS shows gray granular pigmentation, dotted vessels, and whitish scales. The detailed differentiation between Lichen striatus and Lichen nitidus is given in the Table 1.Table 1: Differentiation between lichen striatus and lichen nitidusAlthough there are multiple case reports of LN in blaschkolinear fashion, the LS-like variant of LN is not yet defined. Our patient had hypopigmented macules and patches in blaschkolinear pattern resembling LS; relative chronic nature of lesions and dermoscopy led us to consider LN as a differential diagnosis. IHC findings with positive CD68 staining are similar to the observations made by Dabas et al. on LN and signify the mixed nature of the inflammatory infiltrate in LN. These macrophages play a role in immune response, potentially contributing to the recruitment of the other immune cells and the modulation of the T-cell response.[2] The presence of loosened marginal lesions, arranged in a linear pattern and being inherent in this blaschkolinear lesion, could be explained by the notion that these marginal areas represent an admixture of mutant and nonmutant cells. This would reflect the migration of stem cells during embryogenesis.[3] The view of blaschkolinear manifestations of multifactorial polygenic diseases (BLMMPD) expands the concept of blaschkolinear distribution and superimposed segmental distribution: (i) type Aα, isolated blaschkolinear lesions of a disease nosologically characterized in a nonsegmental manner (e.g., blaschkolinear psoriasis), (ii) type Aβ, isolated blaschkolinear lesions of a disease defined by its Blaschko-linearity (e.g., LS), (iii) type Bα, blaschkolinear lesions with nonsegmental skin lesions of the same type (e.g., blaschkolinear psoriasis plus nonblaschkolinear psoriatic lesions), and (iv) type Bβ, blaschkolinear lesions with nonsegmental skin lesions of distinct cutaneous or extracutaneous manifestations (e.g., blaschkolinear calcinosis cutis in a patient with otherwise typical dermatomyositis).[4] The present case of blaschkolinear LN is an example of type Aα of BLMMPD. There are few reports of LN concurrently occurring with LS. Although LN is a clinical diagnosis, dermoscopy and histopathology help to clinch the diagnosis in the cases with varied clinical presentations. This case highlights the diagnostic challenge presented by LN masquerading as LS. Dermoscopic findings and histopathological examination were crucial in establishing the correct diagnosis. Given the paucity of literature on LN presenting like LS, this case highlights the importance of considering it in differential diagnoses. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. 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