Genital psoriasis coexisting with oral lichen planus – A diagnostic dilemma differentiated by dermoscopic evaluation: A case report

INTRODUCTION

Psoriasis and lichen planus (LP) are inflammatory skin disorders where immunological mechanisms play a major role. Psoriasis is a chronic inflammatory condition involving the skin and joints, with a genetic predisposition, marked by increased activation of innate immune pathways, a T helper (Th)1/Th17-driven adaptive immune response, robust expression of pro-inflammatory cytokines (such as interleukin [IL]-17, IL-22, tumor necrosis factor [TNF- a], and interferon [IFN]-c), and hyperproliferation of keratinocytes.^[1] Plaque, linear, guttate, follicular, and pustular are among the clinical presentations.

LP is an autoimmune skin condition that affects the skin, mucous membranes, hair, and nails. Classical LP, oral LP, hypertrophic LP, LP pigmentosus, and linear LP (LLP) are some of the clinical presentations.^[1,2] Autoreactive cluster of differentiation 8 plus T (CD8+ T) cells that cause keratinocytes to undergo apoptosis are indicative of the disease.^[1]

Both diseases are categorized as papulosquamous disorders; they both show abnormal keratinocyte differentiation and can develop lesions in response to skin traumas or scratching (a phenomenon called the Koebner phenomenon). Despite these similarities, significant differences in distribution, immunological responses, histological features, and associations with major histocompatibility antigens suggest that distinct mechanisms underlie the pathogenesis of these two diseases.^[2]

Psoriasis and LP coexistence is not unusual, but it has been documented infrequently.

In this report, we present a case of genital psoriasis coexisting with oral LP in a patient, which was clinically diagnosed and evaluated and differentiated through dermoscopy, thereby eliminating the necessity for histopathological examination.

CASE REPORT

A 58-year-old woman presented with complaints of a violaceous plaque associated with erosion over the lower lip since 7 years and scaly plaque over the mons pubis and bilateral labia majora since 3 years. It was associated with intense itching. There was no history of any preceding trauma, any recent drug intake, dental metal fillings, hepatitis, or any other infection and joint pains. The patient denied a family history of similar lesions. Family history was unremarkable for any other dermatological autoimmune conditions. She denied any history of fever, sore throat, or upper respiratory tract infection. There was no history of any other autoimmune disease such as vitiligo or autoimmune thyroiditis. An associated uterine prolapse was present.

Clinical examination revealed a violaceous scaly plaque over the lower lip associated with erosion [Figure 1]. On further examination of oral mucosa, buccal mucosa was spared. Rest of the mucous membrane were also examined. It revealed that the genital mucosa was spared but an erythematous scaly plaque with well-defined regular margins was present over the mons pubis and bilateral labia majora [Figure 2]. Scalp was not involved in this patient.

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Figure 1:

Figure showing a violaceous scaly plaque over the lower lip associated with erosion.

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Figure 2:

Erythematous scaly plaque with well-defined regular margins present over the mons pubis and bilateral labia majora.

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Based on the history and clinical examination, provisional diagnosis of oral LP and genital psoriasis was made. The lesions were then evaluated dermoscopically.

Dermoscopy of lesion over the lower lip showed whitish streaks over an erythematous to violaceous background (Wickham striae) which corresponds histologically to focal thickening of the granular layer surrounded by radial linear capillaries [Figure 3].

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Figure 3:

Dermoscopy of lesion over the lower lip showing whitish streaks over an erythematous to violaceous background (Wickham striae) (suggestive of lichen planus) ( Polarised, 38.2x).

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Dermoscopic findings of lesions over the genitalia revealed white scales and regularly spaced red dotted blood vessels on a light red background which corresponds histologically to the dilated vessels. The absence of Wickham striae in dermoscopy can be correlated with the absence of granular layer in psoriatic lesions [Figure 4].

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Figure 4:

Dermoscopic figure showing white scales (black circle), and regularly spaced red dotted blood vessels (black arrow) on a light red background (black star) (suggestive of psoriasis), (Polarised, 32.9x).

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Histopathology could not be done since the patient did not give consent for the same. Hence, a clinical diagnosis was made that was substantiated by dermoscopic findings.

DISCUSSION

We herein document a rare case of the simultaneous occurrence of genital psoriasis and oral LP which was diagnosed clinically and differentiated by dermoscopy. Coexistence of genital psoriasis and oral LP is rare and hence reported.

It is rare for psoriasis and LP to occur simultaneously, as the genetic susceptibility to psoriasis provides an unfavorable predisposition to LP development. A significant role of IFN-y, which is released from activated T cells, has been suggested in the development of LP. On the other hand, IFN-y has been shown to have therapeutic effects in psoriasis patients.^[2]

One of the basic pathogenic mechanisms of LP has been suggested to be an autoimmune attack by CD4+ cells that have cytolytic activity on the epidermal basal cells. Injury to the basal layer, where the epidermal stem cells reside, may lead to a reduction in epidermal turnover, subsequently resulting in an increase in size of keratinocytes and retention of granular layer.^[3] Recent research indicates that in psoriasis, cluster of differentiation 4 plus (CD4+) cells may be associated with the hyperproliferation of the epidermis. Therefore, CD4+ cells are implicated in the pathogenesis of both conditions. Furthermore, the affected skin from either LP or psoriatic lesions demonstrates the presence of CD4+ T cells within the dermal infiltrate.^[3]

Consequently, altered cytokines, autoimmunity, and the Koebner phenomenon have been identified as pathogenetic factors linking LP and psoriasis.^[4] Concurrent activation of both CD4+ and CD8+ T cells has been proposed in the cooccurrence of psoriasis and LP, alongside the upregulation of pro-inflammatory molecules, including TNF-a, INF-a, IL-1, IL-6, IL-22, IL-23, and nuclear factor-kappa light chain enhancer of activated B cells.^[4] Stress, viral infections such as hepatitis C, and certain medications like beta-blockers and angiotensin converting enzyme inhibitors (ACE) inhibitors can act as triggers for both psoriasis and LP. Both conditions exhibit a significant genetic component, and exposure to environmental risk factors, including ultraviolet radiation, smoking, or obesity, may further contribute to the co-occurrence of psoriasis and LP. Individuals suffering from autoimmune disorders, such as rheumatoid arthritis, lupus, or thyroid disorders, are at an increased risk of developing multiple autoimmune skin conditions, including psoriasis and LP.

Gutte detailed the colocalization of LLP and psoriasis vulgaris.^[5] Ohshima et al. identified 12 cases of psoriasis among 711 patients with LP.^[6] Poljacki et al. discovered five cases of LP among 1743 psoriasis patients.^[7] Inalöz et al. documented a case of bullous LP that developed at the skin graft donor site of a patient with psoriasis.^[8] McGimpsey and O’Brien reported a case of oral LP that occurred concurrently with psoriasis.^[9]

In a study by Ujiie et al., psoriasis and LP developed on vitiligo vulgaris lesions – further indicating the role of autoimmunity in causation.^[10]

In our case, dermoscopy proved effective in distinguishing between the two conditions. Dermoscopic findings of lesions over the genitalia revealed regularly spaced red dotted blood vessels which were consistent with findings seen in psoriasis. Dermoscopy of lesion over the lower lip showed whitish streaks over an erythematous to violaceous background which was consistent with the findings seen in LP.

In a study conducted by López et al., a vascular feature (homogeneous red globules) was the most significant dermoscopic finding in the psoriasis dermoscopic pattern. A non-vascular feature (whitish striae) was identified as the most significant dermoscopic feature in the LP pattern.^[11] Wickham striae is the hallmark of LP, primarily observed during active phases, and tend to disappear following treatment; therefore, their presence may be regarded as an activation marker.^[12]

In his study, Lallas et al. assessed the accuracy of dermoscopic criteria for diagnosing psoriasis and LP.^[13] His study indicated that, dotted vessels arranged regularly against a light red background along with white scales were strongly indicative of psoriasis (88.0% specificity and 84.9% sensitivity). Furthermore, whitish lines (Wickham striae) were exclusively observed in LP.^[13]

Thus, in this patient, the diagnosis was made clinically and substantiated by dermoscopic findings.

CONCLUSION

Coexistence of oral LP and genital psoriasis is rare and hence reported for its unusual occurrence. Dermoscopy can be a useful non-invasive investigation to differentiate between two different diseases coexisting in a patient, obviating the need of invasive procedure such as biopsy.