Can Dermoscopy and Ultrasonography be Considered a Prognostic Tool in Management of Psoriasis?

Background: Dermoscopy can reliably predict the diagnosis of plaque psoriasis. Ultrasonography has been increasingly used in dermatology in inflammatory diseases like psoriasis as a tool for evaluation. Hence, this study was done to evaluate the role of dermoscopy and ultrasonography as prognostic aid in plaque psoriasis. Aims and
Objectives: To study the sonographic and dermoscopic findings of clinically diagnosed psoriatic lesions and the changes in the psoriatic lesions if any, with the treatment. How these findings can be utilized to assess the prognosis in these patients. Materials and
Methods: The present study comprised 50 patients with clinically diagnosed plaque psoriasis. Lesions were assessed with Dino-Lite digital microscope AM7515MZT, followed by ultrasonography using a 15 MHz probe, and findings were recorded. All the patients included in this study were given appropriate treatment (topical/systemic) for 6 weeks and were followed up twice i.e., at 3 weeks and 6 weeks after initiating treatment.
Results: Whitish scales were the most common scale color seen in our study seen in 35/50 patients (70%). All the vascular structures were reddish, red dots and globules being the predominant type and with the improvement of the lesions, brown structures increased. A total of 28 (56%) patients had a regular pattern of vessel arrangement. Mean capillary size was 0.097 ± 0.012 mm that reduced to 0.075 ± 0.019 mm at the end of the third week and 0.027 ± 0.032 mm at the end of 6 weeks. In ultrasonographic assessment, mean epidermal thickness reduced from 0.1008 to 0.0764 cm at third week and 0.068 cm at the sixth week, and mean dermal thickness reduced from 0.2692cm to 0.1906cm at the third week and then to 0.1906cm 0.1806cm at the sixth week. In our study, clinical improvement preceded dermoscopic improvement. Newer structures identified in the study are a perifollicular arrangement of capillaries and the presence of lacunar structures in the healing lesions.
Conclusion: The scale distribution, capillary number, and capillary size in dermoscopic assessment, and epidermal and dermal thickness in ultrasonography showed statistically significant changes with treatment and thus may be taken as the prognostic indicators. Thus, both these noninvasive modalities may be useful in the therapeutic monitoring of plaque psoriasis. Copyright:

Introduction

Psoriasis is a common, chronic, inflammatory, and proliferative condition of the skin, associated with systemic manifestations in many organ systems.[1] Although the diagnosis of psoriasis is usually clinical, dermoscopy is often used to diagnose psoriasis thus avoiding the need for histopathological examination. But studies on how such a valuable diagnostic modality can be utilized for the assessment of plaque psoriasis with treatment are rare. Recently, high-resolution ultrasound imaging is increasingly being used in various cutaneous diseases. In the present study, we analyzed the dermoscopic and ultrasonographic findings in plaque psoriasis and the effect on morphological and vascular changes with treatment.

Materials and Methods

Fifty patients of either sex with a clinical diagnosis of plaque psoriasis were enrolled in the study. Patients who were on topical or systemic treatment were excluded from the study. Psoriasis Area Severity Index (PASI) score was calculated before starting the treatment (0 weeks/1st visit) and at every subsequent visit (3rd week and 6th week) after starting appropriate treatment. Since all the psoriatic plaques in an individual responded similarly with the treatment, one plaque representative of the patient's psoriatic lesions was chosen and noted. Only the plaque representative with a typical appearance (i.e., scaling, erythema, and induration) was evaluated. Typical plaques over extremities were preferred over those in the trunk as the former causes the least interference with deeper vascular structures in the Doppler study. The same plaque was evaluated at each visit for the changes if any with the treatment. The selected plaque was cleaned with spirit to reduce the artifact. Videodermoscope attached to the laptop (Dino-Lite AM7515MZT edge series) was placed over the plaque to analyze the characteristics of the scales (scale color, distribution). “Dermoscopic Auspitz Sign” was performed.[2] Ultrasonography gel was applied over the plaque for better visualization of the vascular structures. The type of vessels, their arrangement, and the number per unit area were studied in lower magnification. At higher magnification, the morphology and size of the individual vessels were studied.

Variables included in the dermoscopic analysis were as follows:

Scale color: Whitish, whitish to yellowish, whitish to grayish, yellowish, and grayish.

Scale distribution: Diffuse, patchy

Background color: Dull red, light red, pinkish to brownish, and brown.

Type of vascular structures: Red dots, red globules, red dots and globules, red dots with red linear structures, red and brown dots, brown dots, brown globules, red and brown dots and globules, brown structureless areas.

Vessel arrangement: Regular, regular with ring pattern, regular with linear pattern, regular with a linear and perifollicular pattern, regular with rings (whorled), and perifollicular pattern.

Vessel morphology: Bushy, twisted red loops, bushy with twisted red loops, bushy with hairpin loops and twisted red loops, brownish lacunae with central red globules, brown lacunae with a central brown globules, brown lacunae with central red and brown globules, pale lacunae with central brown globule, pale lacunae with central red and brown globule, empty brown lacunae.

Capillary size and number of vessels per unit area.

The same plaque chosen for dermoscopy was taken for the ultrasonographic examination with a B-mode high-resolution (15 MHz) USG probe. The ultrasound transducer was gently placed over the examination area with the transducer placed perpendicular to the surface with a good amount of gel applied to the skin to provide a correct acoustic interface. After assessing the epidermal and dermal thickness of psoriatic plaque and adjacent normal skin (control), Doppler ultrasonography was done to assess the blood vessels. The arterial resistivity index (also called resistance index, abbreviated as RI), is a measure of pulsatile blood flow that reflects the resistance to blood flow caused by microvascular bed distal to the site of measurement.[3] The presence of vascularization, velocity, and RI were calculated.

Since there are no common parameters assessed using dermoscopy and ultrasonography, it was difficult to statistically compare both modalities. But, we individually studied the changes that appeared in the plaque representative with both the modalities before and after the treatment. Results were tabulated and statistically analyzed.

Results

Demographic profile of the study is shown in Table 1.

Table 1

Summary of clinical data of the patients with plaque psoriasis

Clinical Parameters	Categories	Frequency (n)	Percentage
Age distribution	10-20	5	10
	21-30	9	18
	31-40	12	24
	41-50	9	18
	51-60	13	26
	61-70	1	2
	>70	1	2
Gender Distribution	MALE	35	70
	FEMALE	15	30
Age of onset of psoriasis	1-10	2	4
	11-20	7	14
	21-30	16	32
	31-40	9	18
	41-50	7	14
	51-60	9	18
Duration of illness	<1	6	12
	1-5	23	46
	6-10	9	18
	11-20	8	16
	>20	4	8
Family history	Positive	4	8
	Negative	46	92

Dermoscopic assessment of psoriatic plaque.

In lower magnification (<20×), the commonest scale color analyzed in our study was whitish in 35/50 (70%) patients, whereas yellowish and grayish colored scales were seen in 1/50 (2%) patients only. A combination of whitish with yellowish color and whitish with grayish color was observed in 11 (22%) and two (4%) patients only. Scale color remained the same throughout the study [Table 2].

TABLE 2

Summary of dermoscopic findings in patients with plaque psoriasis

Variables	0TH WEEK	3RD WEEK	6TH WEEK
Scale color	Whitish		35
	Whitish-yellowish		11
	Whitish-grayish		2
	Yellowish		1
	Grayish		1
Scale arrangements	Diffuse	46	28	6
	Patchy	4	22	38
	No scales	0	0	6
Background color	Brown	0	2	34
	Pinkish- brownish	0	26	16
	Light red	11	20	0
	Dull red	39	2	0
Type of vessel (low magnification)	Red dots	13	10	4
	Red globules	3	0	0
	Red dots + red globules	32	3	2
	Red dots + red linear structure	2	0	0
	Red dots + brown dots	0	24	5
	Brown dots	0	7	32
	Brown globules	0	0	1
	Red & brown dots + globules	0	4	6
	Brown structureless areas	0	2	0
Arrangement of vessels	Regular	28	28	40
	Irregular	4	14	10
	Regular + rings	2	2	0
	Regular + linear	6	4	0
	Regular + linear + perifollicular	6	0	0
	Regular + ring + perifollicular	3	0	0
	Cannot assess	1	2	0
Vessel morphology	Bushy	26	17	2
	Twisted red loops	4	0	0
	Bushy + twisted red loops	14	0	2
	Bushy + hair pin loops + twisted loops	3	2	0
	Cannot assess	5	2	2
	Brownish lacunae + central brown globule	0	5	0
	Brownish lacunae + central red globule	0	9	7
	Brownish lacunae + central red & brown globule	0	6	7
	Pale lacunae + brown globule	0	3	2
	Pale lacunae + red globule	0	2	2
	Pale lacunae + red & brown globule	0	2	0
	Empty brown lacunae	0	0	26
	Nil	0	2	0
	Mean vessel number	30.81	27.81	12.49
	Mean capillary size (mm)	0.097±0.012	0.075±0.019	0.027±0.032

Majority of the patients 46/50 (96%) had diffuse scaling that became patchy in 38/50 (76%) patients at the end of the study. Furthermore, 6/50 (12%) patients did not show any scaling at the end of the study.

At lower magnification, capillary types in the form of red dots and globules dominated the picture in 32/50 (64%) patients. However, with treatment increased number of brown structures were observed. The most common vascular structures observed in the third week of the study were red dots intermingled with brown dots in 24/50 (48%) patients followed by only red dots in 10/50 (20%) patients.

Appearance of brown structures was indicative of improvement in the lesion, which was seen in 40/50 (80%) of our patients at the end of the study (i.e., 6 weeks) [Table 2].

Vascular arrangement was regular in the majority 28/50 (56%) of our patients. Along with regular arrangement of dots/globules/both, few areas of the study plaque were showing ring or whorled pattern in 2/50 (4%) patients, linear pattern in 6/50 (12%) patients, and perifollicular arrangement in 6/50 (12%) patients. However, we were unable to comment on the vascular structures in one patient (2%) due to thick scales covering the lesion [Table 2].

At higher magnification, we could visualize bushy capillaries in 26/50 (52%) patients [Figure 1]. Other morphologies seen were bushy with twisted red loops in 14/50 (28%) patients, whereas bushy with hairpin loops and twisted loops were seen in 3/50 (6%) patients. Twisted red loops arranged throughout the field were seen in 4/50 (8%) patients. Morphology could not be assessed in three patients (10%) due to thick scales over the plaque obscuring the vessels.

Figure 1

Dermascopic image of the selected psoriatic plaque (high magnification at 60.3×) showing bushy capillaries at 0 week (First visit)

Other scale and vascular characteristics and changes with treatment are given in Table 2.

The mean capillary size was 0.097 ± 0.012 mm that has reduced to 0.075 ± 0.019 mm at the end of the third week and 0.027 ± 0.032 mm at the end of 6 weeks. Mean vessel number was 30.81 ± 7.033 at initiation (1st visit) of the study, which has reduced to 27.81 ± 8.401 at the end of the third week and further reduced to 12.49 ± 14.322 at the end of the sixth week. The mean capillary size and capillary number showed a statistically significant reduction. (P-value = 0.020).

Ultrasonographic assessment of psoriatic plaque.

At the initiation of the study, the mean epidermal thickness of the normal skin was 0.05 ± 0.012 cm (range: 0.03 cm to 0.08 cm), and the mean epidermal thickness of psoriasis plaque was 0.1008 ± 0.0277 cm (range: 0.05 cm to 0.18 cm). Mean dermal thickness of normal skin was 0.149 ± 0.068 cm (range: 0.06 cm to 0.52 cm) and that of psoriasis plaque was 0.2692 cm (range: 0.12 to 0.67 cm) [Table 3]. Thus, there was a statistically significant increase in the epidermal and dermal thickness of psoriatic plaque compared with normal skin [Figure 5].

Table 3

Summary of ultrasonographic findings in normal skin [NS] and psoriatic plaque [PS] in patients with plaque psoriasis

USG MODE	Skin Parameters	0th week (NS)	0th week (PS)	3rd week (PS)	6th week (PS)
B-mode scan	Epidermal Thickness (cm)	0.0500	0.1008	0.076	0.068
	Dermal thickness (cm)	0.1492	0.2692	0.1906	0.1806
Color Doppler	RI	3.027	3.656	4.048	3.794

Figure 5

High-resolution sonography (B-mode) showing control (normal skin) (a) and psoriatic plaque (b). There is evidence of increased epidermal (D3) and dermal thickening (D4) in image B compared with D1 and D2 in image A

Mean epidermal thickness reduced from 0.1008cm to 0.0764 cm at the third week and 0.068 cm at the sixth week and mean dermal thickness reduced from 0.2692 cm to 0.1906 cm at the third week and then to 0.1806 cm at the sixth week. These findings were also statistically highly significant.

Mean resistive index (RI) was 3.027 in normal skin and 3.656 in the psoriatic plaque at the first visit. An increase in the resistive index in the psoriatic skin compared with normal skin was statistically significant (P-value = 0.030). The mean RI increased to 4.048 at the end of the third week but showed a reduction at the end of the sixth week (RI = 3.794) [Table 2].

Discussion

Most common scales noted in our study were white in color that have been reported in other studies also.[45] Though “gray-blue” color of the scales has been described in few studies, none of the studies in the past have described grayish scales.[5] This may be due to the subjective variation in identifying the scale color and the difference in the nomenclature given by different authors. We found that scale color remained the same throughout the study. The scale distribution was diffuse in majority of the patients, i.e., 46/50 (96%), which became patchy in 38/50 (76%) patients who improved clinically at the end of the study. This was found to be statistically significant (P-value = 0.000). Hence, the patchy distribution of the scales can be considered a good prognostic factor.

Most of the patients (32/50, 64%) showed red dots and globules. More incidence of red globular structures identified in our study may be due to the higher magnification of dermoscope used. As observed by others in their study,[6] we also found red globular structures predominating in the plaques of psoriasis over the lower limb and red dots in plaques over other areas. This may be another possible reason for the increased frequency of red globular structures in our study as we have chosen lower limb lesions in the majority of our patients. Brown structures [Figure 3] can be considered as the resolving vascular structures in the psoriatic plaque and brown color may be due to the presence of hemosiderin in the healing vascular structures. Thus, we observed that with clinical improvement, red structures turned brown though these changes were not statistically significant.

Figure 3

Dermoscopic image (higher magnification at 60.3×) at sixth week after treatment showing pale lacunae with central red and brown globule

The ring or whorled, linear, perifollicular vascular pattern found at the first visit was not seen in the subsequent follow-ups indicating that these patterns disappear early with treatment. Red globules arranged in incomplete rings or whorled patterns were previously described by Vázquez López F et al.,[7] which represented a highly specific feature of plaque psoriasis. The significance of this pattern has to be elucidated further. We also have found a new pattern, perifollicular arrangement of capillaries in 9/50 (18%) patients that disappeared early with treatment. The arrangement of vessels in the third and sixth week after starting treatment also showed an increased frequency of irregularly distributed vessels owing to the improvement in the vascular component and asymmetric disappearance of vascular structures.

The change in background color with treatment was not statistically significant. As the assessment of background color is very subjective, the use of computational methods should be considered for the evaluation of background color.[89]

On studying the morphology of individual vessels, bushy capillaries in 26/50 (52%) were the most common type of morphology seen, which is consistent with the previous studies.[5]

The previous studies have mentioned that hairpin loops are present more in the periphery of the lesion but in our study, we found that hairpin loops and twisted red loops were present both in the periphery and in the center sometimes intermingled with bushy capillaries.[51011] Additional morphological features identified in a psoriatic plaque on treatment were red or brown globules inside a brown or pale lacuna [Figure 2]. These findings can help the clinician diagnose psoriasis, especially when the patients present after taking multiple treatments causing a diagnostic dilemma. Even though these findings are less diagnostic for psoriasis, the clinician should keep these patterns in mind before excluding a diagnosis of psoriasis in these situations.

Figure 2

Dermoscopic image of the same psoriatic plaque at third week showing brown lacunae with central red and brown globules (higher magnification at 60.3×)

Reduction in the number and size of the vessels with treatment was statistically significant and thus can be considered as a good prognostic factor.

At the end of the study, seven (14%) patients had attained complete clinical resolution of the lesion but dermoscopic analysis showed the presence of brown dots in these six out of seven patients. This was reported in previous studies also, where 12/24 (50%) patients attained clinical healing at the end of the study but the dermoscopic pictures returned to normal in two patients only.[11] This important finding indicates that clinical improvement precedes dermoscopic improvement and cutaneous microcirculation remains altered for a longer period even when the lesions are clinically resolved. This might help clinicians to make decisions on tapering or continuing the antipsoriatic drugs as there are remnants of vascular structures in the form of red dots in the clinically healed lesions. This finding can be interpreted as a sign of incomplete remission dermoscopically. These patients are susceptible to relapse on tapering the drugs. Thus, dermoscopy can be used to assess the actual remission (no vascular structures) [Figure 4] than apparent remission, thus avoiding premature tapering of medication.

Figure 4

Showing empty brown lacunae at high magnification (60.3×) indicating complete clinical and vascular healing

Scale distribution, vessel number, and capillary size are the characteristics that showed statistically significant changes with treatment, whereas vessel type, arrangement, and morphology did not show changes that are statistically significant. Hence, scale distribution, vessel number, and capillary size would be the better parameters to assess prognosis.

In the ultrasonographic assessment, the increase in the epidermal and dermal thickness of psoriatic plaque was statistically highly significant compared with the normal skin. The significance of the variation in the resistive index needs further evaluation as this was contrary to the expectation of a gradual decrease in the RI with treatment. Thus, we found that ultrasonographic prognostic indicators were the reduction of both epidermal and dermal thickness.

The advantage of ultrasonography of the skin is that the findings are objective, accurate, and easily reproducible, whereas dermoscopic findings are subjective and there can be interobserver variation.

Conclusion

There are a lot of useful observations in the study that can be extrapolated to the daily clinical practice.

Our study indicates that dermoscopy can be used to know the actual remission (no vascular structures) [Figure 4] than apparent remission, thus avoiding premature tapering of medication.

The scale distribution, capillary number, and capillary size in dermoscopic assessment and epidermal and dermal thickness in ultrasonography may be taken as the prognostic indicators.

The novel finding in this study is the presence of lacunar structures in the psoriatic plaques on treatment that need further studies to assess the significance.

Thus, both dermoscopy and ultrasonography may be useful in the therapeutic monitoring of plaque psoriasis.

Ethics approval statement

This study was approved by the institutional ethics committee.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.