Dermoscopy of Psoriasis: A Comprehensive Overview - IBOOLO

Dermoscopy of psoriasis enables non-invasive diagnosis through hallmark patterns: regularly distributed red-dotted vessels, white scales, and a light-red background.

Dermoscopy of Psoriasis: A Comprehensive Overview for Diverse Audiences

In the realm of dermatological diagnostics, dermoscopy has emerged as an indispensable non-invasive technique, offering clinicians an enhanced visualization of the skin's surface and subsurface structures [all sources]. Also known as dermatoscopy or epiluminescence microscopy, this method employs optical magnification and a light source to overcome the limitations of naked-eye examination. By reducing skin surface reflection through the use of immersion fluids or polarized light, dermoscopy allows for a clearer view of subtle morphological details, including pigmentary networks, vascular patterns, and follicular structures. Initially utilized primarily for the evaluation of pigmented lesions and the differentiation of melanoma from benign nevi, the application of dermoscopy has expanded significantly to encompass a wide spectrum of dermatological conditions, including inflammatory skin diseases like psoriasis.

Psoriasis, a chronic, immune-mediated, and recurrent inflammatory skin disease, affects individuals of all ages and can manifest on the skin, nails, joints, and other sites. The hallmark clinical features of psoriasis include erythematous papules and plaques covered with characteristic white scales. With a global prevalence ranging from 0.09% to 11.43%, affecting over 100 million individuals worldwide, accurate diagnosis and effective management of psoriasis are paramount. While the diagnosis is typically established based on its distinctive clinical presentation, uncertain cases may necessitate histopathological examination, an invasive procedure that is often less preferred by patients.

Dermoscopy offers a valuable non-invasive auxiliary tool in the diagnosis and management of psoriasis, proving to be more acceptable to patients and holding broad application prospects. It enables the visualization of morphological details in the epidermis and superficial dermis, such as pigment and vascular structures, which are not discernible with the naked eye. This enhanced visualization aids in improving diagnostic accuracy, particularly in cases with atypical presentations or when differentiation from other dermatoses is required. Furthermore, dermoscopy demonstrates significant potential in the assessment of disease severity, monitoring treatment efficacy, and predicting disease progression, thus contributing to a more comprehensive understanding and management of psoriasis.

This article aims to provide an up-to-date overview of the role of dermoscopy in the diagnosis and differential diagnosis of psoriasis. It will explore the specific dermoscopic features associated with various clinical subtypes of psoriasis and summarize the current knowledge regarding the application of dermoscopy in evaluating disease severity, monitoring treatment responses, and predicting clinical outcomes. By elucidating the key dermoscopic findings in psoriasis, this review seeks to enhance the understanding of this valuable diagnostic modality among manufacturing professionals, engineers with an interest in imaging technologies, medical practitioners, and anyone intrigued by the capabilities of dermoscopy in dermatological practice.

Dermoscopic Features of Psoriasis Vulgaris

Psoriasis vulgaris, the most common clinical subtype, exhibits distinctive dermoscopic characteristics that aid in its identification. These features can be broadly categorized into vascular patterns, scale patterns, and other notable findings.

Vessel Pattern:

Regular Arrangement of Red-Dotted Vessels: This is the most frequently observed vascular feature in psoriasis vulgaris. First described as symmetrically arranged pinpoint-like capillaries, this pattern is often referred to as dotted vessels, globular vessels, red dots, or red globules. Histopathologically, these correspond to the apical ends of vertically running dilated vessels distributed regularly within the club-shaped dermal papillae. Studies have reported the presence of red-dotted vessels in 96.0% to 100% of patients with psoriasis vulgaris, with approximately 55.6% to 90% exhibiting a uniform distribution. While dotted vessels are common, they are not exclusively seen in psoriasis; however, the regular distribution of these vessels has been found to have a diagnostic specificity of 100% for psoriasis when differentiating from other inflammatory skin diseases where dotted vessels might appear non-homogeneously. The frequency of dotted vessels may be lower in palmar and plantar areas and higher with regular distribution in intertriginous regions, while appearing patchy on the back. Patients with darker skin types may show a lower frequency of these specific vascular patterns.

Ring/Hairpin-Like Vessels: These were first described as round capillaries (red globules) arranged in irregular circles or rings with a beaded, lacelike appearance. Histologically, this pattern represents tortuous, plentiful, coiled, ectatic, and elongated capillaries within the thin, elongated psoriatic dermal papillae. Although observed in a smaller percentage of psoriasis vulgaris cases (3.6% to 44.1%), the presence of ring-like vessels (specificity 94.6% to 100%) and hairpin-like vessels (specificity 91.9%) is highly significant in the diagnosis of psoriasis vulgaris.

Scale Pattern:

White Scale: A hallmark of psoriasis, white scales under dermoscopy correspond to orthokeratosis and/or parakeratosis in histopathology. White scales have a diagnostic specificity of 83.8% for psoriasis vulgaris and are observed in 64.7%–88.3% of patients. They are most commonly found on the scalp and palmar/plantar regions, while less frequent on the face, intertriginous areas, and genitals. The distribution is mainly diffuse or patchy, with patchy distribution more common in younger lesions (<5 weeks) and diffuse in older lesions.

Yellow Scale: Observed in some patients (2.0% to 25.2%), yellow scales may occur with or without white scales and are more prevalent in patients older than 50 years, potentially due to decreased skin turnover and increased orthokeratotic hyperkeratosis with age.

Other Features:

Light Red Background: This is the most common background color in psoriasis, sometimes described as milky pink in children. It correlates with epidermal thinning above the dermal papilla, dilated vessels in the dermal papilla and superficial dermis, and perivascular inflammation. The bright-red background has a sensitivity of 71.0% to 78.0% and a specificity of 53.0% to 75.7%.

Hemorrhagic Dots: These dermoscopic manifestations, also known as the Auspitz sign or bleeding foci, are distinct from the dotted vessels. Observed in around 30% of psoriasis patients, they are common on the lower legs and forearms and may be related to blood extravasation due to venous stasis and scratching.

In conclusion, the most indicative dermoscopic pattern of psoriasis vulgaris comprises regularly arranged dotted vessels over a light red background, accompanied by diffusely distributed white scales. The presence of all three features significantly increases the likelihood of psoriasis vulgaris diagnosis, with high specificity (88.0%) and sensitivity (84.9%). This specific dermoscopic pattern exhibits minimal variation across different lesion sites and skin phototypes, underscoring the great clinical value of dermoscopy in diagnosing psoriasis vulgaris.

Dermoscopic Features of Different Types of Psoriasis

Beyond psoriasis vulgaris, dermoscopy plays a crucial role in identifying and differentiating other clinical variants:

Nail Psoriasis: Dermoscopy demonstrates high accuracy in diagnosing nail psoriasis, with significant agreement between clinical, dermoscopic, and histopathological findings. It enhances the visualization of features like pitting, subungual hyperkeratosis, salmon patches, and splinter hemorrhages compared to clinical evaluation alone. The pseudofiber sign and dilated hyponychial capillaries are often exclusively visible with dermoscopy. Dermoscopy also helps in identifying nail matrix involvement (deep pitting, red spots in the lunula, leukonychia, Beau's lines, onychorrhexis) and nail bed involvement (salmon patch/oil drop sign, onycholysis, splinter hemorrhage, dilated hyponychial capillaries, subungual hyperkeratosis).

Palmoplantar Psoriasis: The most common dermoscopic finding is diffuse white scales. While dotted vessels and a light-red background may be present, they are less frequent than in other locations, likely due to thicker epidermis hindering visualization. Dotted vessels arranged in a beaded pattern along the sulci cutis are a significant diagnostic clue.

Scalp Psoriasis: Similar to psoriasis vulgaris, the most common vascular pattern is red dot/bulb vessels, but twisted red loops are more prevalent. White, thick, diffuse or patchy scales are frequently observed. Signet ring vessels and hidden hair may further support the diagnosis.

Erythrodermic Psoriasis: Dermoscopic patterns reported in limited cases are consistent with psoriasis vulgaris, featuring regular red-dotted vessels, a light-red background, and white scales.

Inverse Psoriasis: Characterized by well-defined erythematous plaques in flexural areas with minimal or absent scales, dermoscopy typically reveals regularly distributed dotted vessels on a reddish background.

Guttate Psoriasis: Exhibiting erythematous papules/small plaques with white scales, dermoscopy shows regularly distributed dotted vessels in a reddish background, similar to plaque psoriasis but potentially less pronounced due to smaller lesion size.

Pustular Psoriasis: Dermoscopy reveals regularly distributed dotted vessels with milky globules (representing sterile pustules) on a reddish background. The non-follicular localization of pustules is a key observation.

Dermoscopic Differential Diagnosis of Psoriasis

Dermoscopy significantly aids in differentiating psoriasis from other skin conditions that may present with similar clinical features.

Differential Diagnosis of Psoriasis Vulgaris: Dermoscopy helps distinguish psoriasis vulgaris from conditions like lichen planus (linear vessels, peripheral distribution, Wickham striae), pityriasis rosea (patchy dotted vessels, peripheral fine white scales, brown globules, collarette sign), mycosis fungoides (short, fine, linear or spermatozoa-like vessels, geometric fine white scales, orange-yellow patches), and pityriasis rubra pilaris (dotted and linear vessels, perifollicular yellow/orange halos, follicular plugs with central hair).

Differential Diagnosis of Nail Psoriasis: Dermoscopy assists in differentiating nail psoriasis from onychomycosis (spikes, ruin pattern, longitudinal streaks, distal irregular termination), traumatic onycholysis (regular and smooth line of detachment), and allergic contact dermatitis due to artificial nails (onycholysis with a dented border, periungual tissue damage).

Differential Diagnosis of Palmoplantar Psoriasis: Dermoscopy aids in distinguishing it from palmoplantar eczema (patchy dotted vessels, dull red or yellow background, brown or orange dots/globules, yellow crusts) and palmar syphiloderm (orange background, circular scaling edge with erythematous halo - Biett sign).

Differential Diagnosis of Scalp Psoriasis: Dermoscopy helps differentiate it from seborrheic dermatitis (arborizing red lines, comma vessels, twisted red loops less common, yellowish background, fine greasy scales). Key differentiating features include vascular patterns and scale characteristics.

Differential Diagnosis of Pustular Psoriasis: Dermoscopy can differentiate it from acute generalized exanthematous pustulosis (AGEP) by the presence of regularly distributed dotted vessels in pustular psoriasis, which are typically absent in AGEP.

Differential Diagnosis of Erythrodermic Psoriasis: Dermoscopy can help distinguish it from erythrodermic atopic dermatitis (yellowish globules, patchy dotted vessels) and erythrodermic mycosis fungoides (linear and dotted vessels on a pale pinkish background, spermatozoa-like vessels).

Assessment of Therapeutic Effect and Severity in Psoriasis by Dermoscopy

Dermoscopy provides valuable insights into disease severity and treatment response.

Assessment of Severity: The Vascular Psoriasis Area Severity Index (VPASI) has been proposed based on dermoscopic vascular patterns. While correlations between PASI/BSA and specific dermoscopic features are not consistently observed, dermoscopy of the nail area shows promise, with features like nail plate thickening correlating with NAPSI scores and systemic inflammation.

Assessment of Therapeutic Effect: Changes in vascular patterns in psoriasis vulgaris, such as decreased diameter and density of dotted/globular vessels, correlate with clinical improvement. In nail psoriasis, a decrease in visible capillaries after treatment and improvement in dermoscopic features like scaling and hemorrhages indicate positive treatment response.

Prediction and Monitoring in Psoriasis by Dermoscopy

Dermoscopic features can predict treatment outcomes and monitor for recurrence.

Prediction of Therapeutic Outcome: Globular vessels may be associated with treatment resistance, while dotted vessels predict better outcomes with local treatments. The appearance of hemorrhagic dots may predict a favorable response to biological agents. Specific nail dermoscopic features can also predict treatment outcomes in nail psoriasis. The appearance of red linear vessels under dermoscopy in patients using long-term topical steroids may predict impending steroid-induced skin atrophy.

Monitoring and Prediction of Recurrence: The persistence of dotted vessels under dermoscopy after clinical remission is associated with a higher risk of recurrence, suggesting the concept of "dermoscopic healing". The recurrence of dotted vessels may also predict clinical relapse after treatment with biological agents.

Study Limitations

Current research on dermoscopy in psoriasis has limitations, including a limited amount of literature and the need for larger, multicenter studies. Furthermore, inconsistent terminology used to describe dermoscopic manifestations, particularly in nail psoriasis and treatment outcome prediction, necessitates standardization.

Dermoscopy stands as an economical, non-invasive, and rapid examination technique with significant clinical value in the diagnosis and differential diagnosis of psoriasis. It holds great promise for severity assessment, efficacy prediction, and monitoring disease course. While dermoscopy in psoriasis is still in an exploratory phase due to its relatively short development time, ongoing large-scale research is crucial to establish definitive diagnostic criteria and further elucidate the underlying mechanisms. As the "stethoscope of dermatologists", dermoscopy provides a valuable bridge between clinical observation and microscopic pathology, ultimately improving diagnostic precision and enhancing patient care in psoriasis management.

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