Dermoscopy of lichen nitidus: a study of 20 cases

INTRODUCTION

Lichen nitidus (LN) is a chronic inflammatory lichenoid dermatosis, more commonly seen in childhood or early adulthood. It is characterized by development of pinpoint to pinhead‐sized papules, which are usually asymptomatic and skin‐coloured to hypopigmented, with a flat, shiny surface. The sites commonly involved are upper extremities, trunk, buttocks, and genitalia, with occasional involvement of nails and palms and soles. The common clinical differentials that need to be differentiated are lichen scrofulosorum, follicular eczema, follicular psoriasis, keratosis pilaris and PMLE. The diagnosis can be confirmed through histopathological examination which shows a flattened parakeratotic epidermis with acanthotic rete ridges extending downwards like a claw clutching a ‘ball like’ lymphohistiocytic inflammatory infiltrate, giving a characteristic “ball in claw appearance.” Basal cell hydropic degeneration is also seen in some cases.¹ Knowledge of dermoscopic features of LN can be a valuable non-invasive and painless diagnostic aid to differentiate and rule out clinical mimics, especially in children where an invasive method like biopsy may not always be feasible. Therefore, through this study, we identify newer dermoscopic patterns seen in LN, dermoscopic patterns with respect to different clinical variants and duration of disease, and histopathological correlation of dermoscopy findings.

CASE SERIES

In a span of 6 months, 20 patients of LN were studied. Only biopsy proven cases of LN were included in the study. Clinical features (age, sex, duration, symptoms, morphology and site) were recorded. Dermoscopy was done in both non polarized and polarized modes using were studied using a self-illumination digital dermatoscope Dino-lite AM4113/AD4113 series. Dermoscopic features were studied and correlated clinically.

The mean age was 25.7 years with a range of 6-65 years. 50% patients were in the pediatric age group. 45% and 55% patients were male and female, respectively. The median duration of disease was 6 months with a range of 7 days to 2 years. In symptomatology, 55% patients were asymptomatic while 45% complained of itching. Forearms, arms, dorsal aspect of hands and back were the most common sites in the decreasing order of the frequency.

Koebner phenomenon was seen in 60% cases and associated atopy in 40% cases. Associated diseases like psoriasis and lichen planus was seen in 5% and 15% patients, respectively. Nail involvement was seen in 45% patients.

The clinical variants seen were generalized (60%), actinic (20%), palmoplantar (15%) and follicular (5%) (Figure 1).

Dermoscopic findings seen on non-polarizing and polarizing modes are depicted in Table 1. The findings seen on non-polarizing mode were-shiny elevated surface with absence of skin markings (100%), scaling (70%), radial ridges (50%) and central depression (35%) (Figure 2). Findings seen on polarizing mode were-hypopigmentation (100%), brown shadow (70%), linear vessels (65%), accentuation of surrounding reticulate pigment network (65%), diffuse erythema (45%) (Figure 3).

The newer dermoscopic findings seen are depicted in Table 2.

Two types of pigmentary patterns were seen: central grey-brown structureless areas (30%) and speckled brown pigment (40%). Newer vascular patterns seen were curvilinear vessels (50%), branching/serpentine vessels (20%), radial vessels (10%). Other patterns seen were white dots and streaks (30%) and ring-in-ring appearance (5%) (Figure 4 and 5).

In the actinic variant, diffuse erythema and brown structureless areas were seen in 75% of the cases. A characteristic “fern-leaf” pattern was seen in 1 case. In the follicular variant, three zones were seen from inside to outside-perifollicular collarette scaling, rim of hypopigmentation and rim of accentuated pigment network. Two patterns were seen in the palmoplantar variant-circular pits with brown rim and circular pits with keratotic plugging (Figure 6).

The dermoscopic findings with respect to the duration of the disease are depicted in Table 3. In acute disease (<6 months), the most common dermoscopic findings were-brown globules and speckled pigment (60%), brown shading (60%), and scaling (60%). In chronic disease (>6 months), the most common dermoscopic findings were linear vessels (80%), brown shadow (80%) and scaling (75%) followed by curvilinear vessels (60%).

DISCUSSION

LN is a chronic inflammatory lichenoid dermatosis, more commonly seen in childhood or early adulthood. It is characterized by development of pinpoint to pinhead‐sized papules, which are usually asymptomatic and skin‐coloured to hypopigmented, with a flat, shiny surface. Sites commonly involved are upper extremities, trunk, buttocks, and genitalia, with occasional involvement of nails and palms and soles.¹ Clinical variants of LN are confluent, vesicular, haemorrhagic, palmoplantar, follicular, perforating, linear and generalized.² Out of these, 4 types of variants were assessed in this series. (Generalized, actinic, palmoplantar and follicular, in decreasing order of frequency.)

There was a slight female preponderance seen. Clinically, 55% patients were asymptomatic while 45% complained of itching, consistent with the previous studies and the asymptomatic nature of illness in general.³ Forearms, arms, dorsal aspect of hands and back were the most common sites in decreasing order of frequency.

Koebner phenomenon and atopy were seen in 60% and 40% cases, respectively. Associated diseases like psoriasis and lichen planus was seen in 5% and 15% patients, respectively. Nail involvement was seen in 45% with longitudinal ridging being the most common finding. Other nail changes seen were subungual hyperkeratosis and pitting. Trachyonychia, longitudinal ridges, transverse ridges, and median canaliform dystrophy are other reported nail changes in LN.

On dermoscopy, on non-polarizing mode the most common findings in decreasing order of frequency were shiny elevated surface with absence of skin markings, scaling, radial ridges and central depression. On polarizing mode, hypopigmentation, brown shadow, linear vessels, accentuation of surrounding reticulate pigment network and diffuse erythema were the most common findings in decreasing order of frequency. Absent skin markings and hypopigmentation were the most common finding seen in 100% cases, with similar results seen in a series of 8 cases.^[4] The second most common finding seen in our study was a central brown shadow and scaling. The patterns of scaling seen were a peripheral collarette and central collarette scaling.

Certain newer dermoscopic patterns in LN were identified. Two types of pigmentary patterns seen: central grey-brown structureless areas and speckled brown pigment. These correlate with the pigment incontinence on histopathology, and are distinct from the central brown shadow which is lighter, more homogenous, and corresponds to the ball like infiltrate on histopathology.

Newer vascular patterns observed in decreasing order of frequency were curvilinear vessels, branching/serpentine vessels and radial vessels, apart from the already described linear vessels of LN, which happened to be the most common vascular pattern. Two other patterns seen were observed- white dots and streaks (30%) and ring-in-ring appearance (5%).

On correlating the dermoscopic findings with clinical variants, diffuse erythema and brown structureless areas were the most common findings in the actinic variant. A characteristic “fern-leaf” pattern was seen in 1 case. The fern leaf pattern has reported previously as a feature of actinic LN, although the authors had concluded that it may be seen in other lichenoid disorders as well.⁵ In the follicular variant, three characteristic zones were seen from inside to outside-perifollicular collarette scaling, rim of hypopigmentation and rim of accentuated pigment network. Two patterns were seen in the palmoplantar variant-circular pits with brown rim and circular pits with keratotic plugging, which has not been reported before. Other findings like ovoid pits surrounded by peripheral silvery scales arranged linearly and multiple pitted punctual hemorrhages, described previously in palmoplantar LN were not seen.^6,7

Dermoscopic evolution of the lesion showed that the early lesions were better appreciated on polarizing mode and the earliest finding being loss of skin markings and hypopigmentation. The radial ridges, central depression, brown shadow and peripheral pigment network accentuation were comparatively less defined or absent in the early lesion as compared to the well-formed lesion.

The dermoscopic findings were also correlated with respect to the duration of the disease. Interestingly, vessels were more commonly seen in chronic cases (> 6 months) while pigmentary patterns were more commonly seen in early disease (< 6 months). This could be due to the pigment incontinence caused by vacuolar degeneration of basal layer in early disease whereas the pressure induced by the focal infiltration may be responsible for the easier visibility of vessels through the atrophic epidermis in the late stages.

On correlating dermoscopic findings with histopathologic findings, the well circumscribed hypopigmented circles corresponded to acanthotic epidermis, central depression & Brown shadow correlated with the focal dense ball like infiltrate, radial ridges (starburst appearance) correlated with elongated rete ridges at the edge of the lesion, loss of skin markings correlated with the flattening of epidermis overlying the infiltrate, peripheral & central scaling correlated with focal parakeratosis, pigment globules and speckled pigment corresponded to pigment incontinence in the upper dermis due to vacuolar degeneration of the basal layer and vascular patterns correlated to dilated vessels in upper dermis visible on dermoscopy due to epidermal atrophy.

CONCLUSION

Being a fairly common disorder seen in childhood, dermoscopic features of LN has not been studied extensively. This series describes the dermoscopic features of LN, with many interesting novel pigmentary and vascular dermoscopic patterns identified. Absent skin markings and hypopigmentation were the most common as well as earliest findings. Vessels were more common in chronic cases while pigmentary patterns were more common in early disease. LN presents fairly distinctive dermoscopic features and dermoscopy can be a non-invasive, painless aid in differentiating it from close clinical differentials and avoid the need for a biopsy, especially in children.

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: Not required

REFERENCES

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