Dermoscopy in the Diagnosis of Palmoplantar Eczema and Palmoplantar Psoriasis: A Cross-Sectional, Comparative Study from a Tertiary Care Centre in North India

Abstract

Introduction:

Palmoplantar hyperkeratotic lesions pose a diagnostic difficulty when differentiating clinically between palmoplantar psoriasis (PPP) and palmoplantar eczema (PPE). Dermoscopy can provide valuable clues in reaching the final diagnosis.

Objectives:

To identify and compare dermoscopic findings seen in PPP and PPE.

Methods:

This was a cross-sectional, comparative study carried out prospectively between March 2019 and June 2020. All adult, consenting patients visiting the dermatology outpatient department who were clinically diagnosed and histopathologically confirmed as PPP and PPE were recruited into two groups. The dermoscopic examination was done, and images were taken from the representative area. The findings were analysed by two dermatologists who were unaware of the diagnosis. The sensitivity, specificity, positive predictive value and negative predictive value of these findings were assessed.

Result:

A total of 81 patients were recruited (39 patients of PPP and 42 patients of PPE). Significant findings seen in psoriatic plaques were the presence of regular vessels (84.6%, P < 0.001), with diffuse scales (87.2%) over a dull red/pink background (69.2%, P < 0.001). Dermoscopy of PPE displayed a significant presence of yellowish scales (76.2%, P < 0.001), with focal (61.9%) or absent vessels (35.7%), brown/orange-brown dots and/or globules (66.7%), yellow/yellow-orange crusts (57.1%) over a yellow/yellow-brown background (88.1%).

Conclusion:

Distribution of vessels, distribution of scales and the colour of scales, presence of brown/orange-brown dots and/or globules, yellow/yellow-orange crust and background colour (dull red vs. yellow/yellow-brown) of the plaques can be useful clues in the diagnosis of PPP and PPE.

Introduction

Palmoplantar skin lesions are one of the chief presenting complaints among patients seen at any dermatology outpatient department. Palmoplantar psoriasis (PPP) and palmoplantar eczema (PPE) negatively affect the patient's quality of life, resulting in significant functional impairment and social stigma.[1,2] Studies have reported PPP to be more disabling compared to psoriasis without palm and sole involvement.[3] Though PPP differs from PPE in that the former usually presents with sharply demarcated lesions without pruritus or vesicles, clinicians face difficulty in accurately diagnosing isolated PPP and PPE owing to their similar clinical presentation, which requires histological analysis to reach a definitive diagnosis.[4,5] Recent literature is rife with increased risk of a plethora of comorbid diseases in patients with psoriasis, including cardiovascular disease, metabolic syndrome and non-alcoholic fatty liver disease, to name a few compared to the general population.[6,7,8] This warrants better differentiation of PPP and PPE. Dermoscopy was conventionally used to assist in diagnosing skin tumours and pigmentary disorders. Its ability to visualize structures invisible to the naked eye (e.g., vessels) has expanded its utility in diagnosing inflammatory diseases, making it the stethoscope of dermatologists.[9,10] Being a non-invasive and rapid procedure, dermoscopy can help decrease the need for an invasive procedure, including biopsy in the diagnosis of PPP and PPE. In the present prospective study, we compared dermoscopic findings in patients of PPP and PPE.

Objectives

This prospective observational study was conducted between March 2019 and June 2020 to study and compare the dermoscopic findings in patients of PPP and PPE.

Materials and Methods

After obtaining approval from the Institutional Scientific Research Protocol Review Committee and Institutional Ethics Committee (Dermatology/2019/02, Reference no: HIMS/RC/2019/55), the study was carried out prospectively from March 2019 to June 2020 for a duration of 15 months.

Adult patients (>18 years of age) attending the dermatology outpatient department with a definite diagnosis of PPP or PPE established by the typical clinical findings (by two independent dermatologists) and confirmed with classic histological features (assessed by the same histopathologist), who were not using any treatment modality in the previous four weeks were recruited consecutively in the study after obtaining written informed consent. A clinical diagnosis typical of PPP was made on the presence of plaques without prior history of exudation with a well-defined border, non-adherent thick scales and symmetrical distribution. The typical clinical findings of PPE were considered to be ill to well-defined plaques over the proximal or middle palm and volar surface of fingers and/or soles.[11,12] The confirmatory histopathological features of PPP were taken to be, namely, the presence of confluent parakeratosis or vertically placed multiple parakeratotic foci, neutrophils in the parakeratotic layers, decrease or loss of granular layer, suprapapillary thinning, presence of tortuous and dilated vessels in the papillary dermis. Histopathological findings of compact hyperkeratosis, plasma mounds in the corneal layer, intact granular layer, frank and widespread spongiosis, with irregular acanthosis were taken to be confirmatory of PPE.[5,12] Patients having palmoplantar pustulosis, positive KOH microscopic examination, non-specific histological findings or in whom the histopathological diagnosis was incongruent with the clinical diagnosis were excluded from the study. Clinical details of the patient, including the total duration of illness, history of atopy, site of involvement, presence of fissures, nail involvement and involvement of other body sites were recorded.

Dermoscopic evaluation

Dermoscopic examination of the target area was done by two independent dermatologists, unaware of the diagnosis using DermLite DL4 (3Gen, San Juan Capistrano, California, USA, 10× magnification) before the histological examination and images were captured via Dermlite adaptor for iPhone X (3Gen DermLite Dermascope Connection Kit for iPhone X; San Juan Capistrano, CA). Dermoscopic findings were analysed and recorded under the following headings: i) presence or absence of vessels and their distribution (focal or diffuse/regular), ii) presence or absence of scales, their colour (white/grey-white, yellowish) and distribution (patchy or diffuse), iii) background colour (dull red, yellow/yellow-brown or mixed) and iv) the presence of yellowish crusts, brown/orange-brown dots and globules, presence of yellowish-white lines or streaks. Ultrasound jelly was utilized as linkage fluid for visualization of underlying structures. The dermoscopic features recorded were based on the findings previously published and the authors’ past observations of dermoscopy of confirmed cases of PPP and PPE.[13,14]

Statistical analysis

Statistical analysis was done using SPSS software version 23. (SPSS, Chicago, IL, USA) Categorical variables were expressed as numbers and percentages, and numerical data were expressed as mean and standard deviation. A comparison of dermoscopy findings was done between PPP and PPE. The categorical variables were compared using the Chi-square test and a P-value of less than 0.05 was considered significant. The sensitivity, specificity, positive predictive value and negative predictive value of dermoscopic findings found to be significantly present in one group were calculated using the other group as a control.

Results

A total of 99 (49 patients of PPP and 50 patients with PPE) cases were biopsied with a clinical diagnosis of PPP or PPE. Of these, 18 (10 patients of PPP and 8 patients of PPE) patients were excluded from the study because of either non-specific histological findings or histopathological diagnosis incongruent with clinical diagnosis. Thus, dermoscopic findings were compared in 81 patients (39 patients of PPP and 42 patients of PPE).

There were 61.5% (24/39) males and 38.5% (15/39) females in the PPP group, with 40.5% (17/42) males and 59.5% (25/42) females in the eczema group (p = 0.076). The age of the patients ranged from 18 to 73 years with a mean age of 44.0 ± 14.7 in the PPP group and the same was 21–75 years and 45.7 ± 13.8 (p = 0.590) in the PPE group. The mean duration of illness in the PPP group was 2.3 ± 2.2 years and the same was 2.2 ± 3.4 years (p = 0.871) in the PPE group. None of the patients with PPP had a history of atopy, whereas a history of atopy was elicited in 45.2% (19/42) patients with PPE (p < 0.001). On comparing clinical characteristics among the two groups, the presence of fissures was seen to be more in the PPE group, which was seen in 59.5% (25/42) patients compared to 41.0% (16/39) patients of PPP (p = 0.121). Nail involvement was encountered in 81.5% (31/38) of patients with PPP compared to its involvement in only 42.8% (18/42) patients in the PPE group (p = 0.001). Seventeen patients of PPP had psoriatic plaques involving other body sites, and five patients of PPE had eczema elsewhere.

Dermoscopy findings of PPP and PPE and their comparison are detailed in Table 1.

Table 1.

Dermoscopic findings seen in palmoplantar psoriasis (PPP) and palmoplantar eczema (PPE)

Dermoscopy characters	PPP (%) (n=39)	PPE (%) (n=42)	P
Vessel distribution			<0.001
Focal	5 (12.8)	26 (61.9)
Regular/diffuse	33 (84.6)	1 (2.4)
None	1 (2.6)	15 (35.7)
Scale distribution			0.037
Patchy	5 (12.8)	14 (33.3)
Diffuse	34 (87.2)	28 (66.7)
Scale colour			<0.001
White/white grey (W/WG)	6 (15.4)	0
Yellowish (Y)	2 (5.1)	32 (76.2)
Both (W/WG+Y)	31 (79.5)	10 (23.8)
Background colour			<0.001
Dull red/pink	27 (69.2)	0 (0)
Yellow to yellow-orange	0 (0)	37 (88.1)
Combination	12 (30.8)	5 (11.9)
Yellow-white linear lines	22 (56.4)	5 (11.9)	<0.001
Brown/orange-brown dots and globules	0	28 (66.7%)	<0.001
Yellow/yellow-orange crust	3 (7.7)	24 (57.1)	<0.001

PPP: palmoplantar psoriasis; PPE: palmoplantar eczema; W/WG: white/grey-white; Y: Yellowish

Distribution of vessels was regular/diffuse in most of the PPP (84.6%, 33/39) patients, whereas it was most commonly focal in PPE cases (61.9%, 26/42) (p < 0.001) [Figures 1–4].

Figure 1.

(a) Clinical image of a patient with PPP; (b) Non-polarized dermoscopic examination showing diffuse white scales in psoriasis; (c) Polarized dermoscopy in the same patient showing diffuse white scales with regular dotted vessels over dull red background; (d) application of ultrasound jelly enhanced visualization of regular dotted vessels; (e) Diffuse yellow and white scales with regular vessels over a dull red background in another patient of PPP (inset: clinical image); (f) Dermoscopy after application of ultrasound jelly showing more prominent regular vessels (black circle) over dull red background (blue star). Yellow-white lines/streaks (black arrow) also seen (Dermlite, 3Gen Inc. DL4, polarized mode, 10× magnification, images captured with Dermlite adaptor for iPhone X)

Figure 4.

(a) Regular dotted vessels seen with patchy white and yellowish scales over a dull red background in dermoscopy of PPP. (inset shows clinical image); (b) Prominent scales seen in non-polarized mode (inset shows clinical image); (c) Polarized mode showing diffuse yellowish and grey-white scales with regular vessels over a dull red background; (d) Regular vessels appreciated more clearly after application of ultrasound jelly; (e) Dermoscopy in polarized mode displaying diffuse scales with dotted vessels (black circle) in a patient with palmoplantar psoriasis. (inset shows clinical image); (f) Dermoscopic examination after application of ultrasound jelly shows the presence of dotted vessels diffusely over a combination of dull red (black star) and yellow-orange background (blue star) (Dermlite, 3Gen Inc. DL4, polarized mode, 10× magnification, images captured with Dermlite adaptor for iPhone X)

Figure 2.

(a) Polarized dermoscopic examination in PPE showing diffuse yellowish scales with yellow crust (black oval) over yellow background. Vessels are not visualized. (inset: clinical image); (b) patchy yellow scales over a yellow background seen in a patient of PPE (inset: clinical image); (c) prominent dots and globules (black arrow) visualized in another patient of eczema; (d) more prominent dots and globules (blue arrow) visualized; (Dermlite, 3Gen Inc. DL4, polarized mode, 10× magnification, images captured with Dermlite adaptor for iphone X)

Figure 3.

(a) Yellowish scales (blue arrow) with prominent orange-yellow crust (black arrow), patchy vessels (black box) seen over a combination of yellow (blue star) and dull red background (black star) (inset: clinical image); (b) polarized dermoscopy showing diffuse yellow scales over a yellow-brown background in a patient of eczema (inset shows clinical image); (c) Polarized examination after application of ultrasound jelly shows fewer yellowish scales with patchy vessels (black circle) visualized over a yellow-brown background. (Dermlite, 3Gen Inc. DL4, polarized mode, 10× magnification, images captured with Dermlite adaptor for iPhone X)

Diffuse scales were seen more in PPP lesions (87.2%, 34/39) compared to PPE (66.7%, 14/42) (p = 0.037). The colour of scales was yellowish in most PPE cases (76.2%, 32/42), followed by a combination of yellowish and white/grey-white scales (23.8%, 10/42), with none of the PPE cases having white/grey-white scales alone. Compared to this, the colour of scales most commonly encountered in psoriatic plaques was the combination of both white/grey-white and yellowish scales in 79.5% (31/39) cases followed by only white/grey-white coloured scales (15.4%, 6/39), and yellowish scales alone (5.1%, 2/39). The background colour most commonly seen in psoriatic patients was dull red/pink (69.2%, 27/39), followed by the combination of dull red/pink and yellow/yellow coloured background (30.8%, 12/39). In PPE, 88.1% (37/42) patients had a yellow/yellow-brown background, with the remaining 11.9% (5/42) having a combination of dull red/pink and yellow/yellow-brown background (p < 0.001). Dermoscopy of PPE displayed brown/orange-brown dots and globules in 66.7% (28/42) cases, whereas none of the psoriatic patients had this finding (p < 0.001). Yellow/yellow-orange crusts were also seen more frequently in PPE (57.1%, 24/42) compared to PPP, where it was appreciated in only 7.7% (3/39) patients (p < 0.001). Yellow-white lines were observed in dermoscopy of both PPP and PPE, with its presence noted more frequently in the PPP lesions (56.4% vs. 11.9%, P < 0.001). Table 2 summarizes the sensitivity, specificity, positive predictive value and negative predictive value of these findings.

Table 2.

Sensitivity, specificity, positive predictive value and negative predictive value of dermoscopic findings

Dermoscopic findings	TP (a)	FN (b)	FP (c)	TN (d)	Sensitivity % (a/a+b)	Specificity % (d/c+d)	PPV (a/a+c)	NPV (d/d+b)
PPP
Regular vessels	33	6	1	41	84.6	97.6	97	87.2
Dull red/pink BG	27	12	0	37	69.2	100	100	75.5
Diffuse white scales	23	16	0	42	59	100	100	72.4
Yellow-white lines	22	17	5	37	56.4	88	81.4	68.5
PPE
Dots and globules	28	14	0	39	66.7	100	100	73.5
Yellow BG	37	5	0	39	88.1	100	100	88.6
Diffuse yellow scales	28	14	11	28	66.7	71.8	71.8	66.6
Yellow/yellow-orange crust	24	18	3	36	57.1	92.3	88.8	66.7

PPP: palmoplantar psoriasis; PPE: palmoplantar eczema; TP: true positive; FN: false negative; FP: false positive; TN: true negative; PPV: positive predictive value; NPV: negative predictive value; BG: background

Discussion

Dermoscopy of 14 cases of palmar psoriasis (PP) was reported to show the presence of regular dotted vessels in 77.3% of cases with diffuse white scales in 68.2% of cases.[14] This finding was further substantiated in a recent study of 10 patients of PP by Errichetti and Stinco,[13] where vessels were seen in 40% of cases, with 80% of cases showing diffuse white scaling. In the present study, we found regular dotted vessels in 84.6% of psoriatic lesions with diffuse scales in 87.2% of cases. We performed a stepwise approach to dermoscopic examination, a sequence starting with non-polarized, non-contact mode, followed by non-contact polarized mode and finally non-contact polarized mode after the application of ultrasound jelly, which can be attributed to greater visualization of vessels in the present study. Regular vessels were seen in only one patient (2.4%) of PPE, similar to a recent study wherein authors found this finding in only 3.6% (2/55) patients with eczema.[15] Based on these observations, we suggest that the presence of regularly distributed dotted vessels should strongly favour a diagnosis of PPP over PPE. While none (0/42) of the lesions of PPE had diffuse white scales compared to its presence in 59.0% (23/39) of PPP cases, diffuse yellow scales were seen in 66.7% (28/42) of PPE lesions and only 28.2% (11/39) of PPP lesions (p = 0.001). Though patchy white/grey white scales were seen in dermoscopy of PPE, when present, they were in combination with yellowish scales in all cases. Upon dermoscopic evaluation, this difference in colour and distribution of scales can be a useful distinguishing feature when differentiating PPP and PPE.

Regarding the background colour, none of the psoriatic plaques in the present study showed a yellow/yellow-brown background alone, though it was seen in combination with dull red/pink background in 12 (30.8%) cases. Similarly, none of the PPE lesions had an underlying dull red/pink background exclusively, with the majority of the patients (37/42, 88.1%) displaying a yellow/yellow-brown background. This is in line with previous studies where dull red was the most common background colour in psoriatic plaques.[15,16] In the present study, brown/orange-brown dots and/or globules were seen in the dermoscopy of 66.7% of PPE cases and none of the PPP cases. This finding is similar to the study by Errichetti and Stinco[13] where brown/orange-brown dots and/or globules were present in 72.7% (8/11) of palmar eczema patients and no patients with PP. Brownish dots and/or globules represent the underlying palmoplantar spongiotic vesicles seen in eczema, which do not rupture easily owing to the thickened corneal layer making it difficult to appreciate with the naked eye. Thus, the visualization of brownish dots and/or globules upon dermoscopic examination strongly point towards a diagnosis of PPE over PPP. In the present study, yellow/yellow-orange crust was another finding noted more commonly in dermoscopy of PPE than PPP (57.1% vs. 7.7%, P < 0.001). This is similar to previously reported studies where yellow crusts were significantly more common in eczema than psoriasis.[13,15] Yellow-white lines seen in the dermoscopy of both PPP and PPE have hitherto not been described with these dermatoses. The presence of these lines was seen more frequently in the PPP group than in the PPE group (56.4% vs. 11.9%, P < 0.001). We believe these yellowish-white lines or streaks represent the underlying parakeratosis and hyperkeratosis, which though can be seen histologically in both conditions, is more commonly seen in psoriatic plaques than eczema.

Though dermoscopy of psoriasis and eczema has been well described, there is a paucity of studies that compare dermoscopic findings of PPP and PPE.[13,15,17] Errichetti and Stinco[13] compared dermoscopic findings in 10 patients with PP and 11 patients with palmar eczema. In another study by Çetinarslan et al.,[15] dermoscopic findings were evaluated in 35 patients with PPP and 55 PPE patients. In the present study, the most common dermoscopic findings in PPP were diffuse scaling with regular vessels. Dermoscopy of PPE most commonly displayed diffuse yellowish scales, brown/orangish-brown dots or globules and yellow/yellow-orange crusts with focal or no vessels. Findings of the studies comparing the dermoscopic findings of PPP and PPE are summarized in [Table 3]. To avoid confusion that can arise when differentiating the underlying background of plaques into light red and dull-red colour, in the present study, the background colour was divided into dual red/pink, yellow/yellow-orange and a combination of both. A dull red/pink background was seen most commonly in PPP and yellow/yellow-brown in PPE [Table 4].

Table 3.

Summary of studies comparing dermoscopic findings of PPP and PPE

First author/journal/year of study/study design	No. of patients of PP/PE	Dermoscopic findings assessed	Frequency of reported findings in PP (%)	Frequency of reported findings in PE (%)
Errichetti, et al. J Dermatol 2016/ Cross-sectional	10/11	White scales:	100	45.5
		Diffuse/Patchy	80/20	0/45.5
		Yellow scales	0	90.9
		Dotted vessels:	40	27.3
		Diffuse/focal	40/0	0/27.3
		Brownish-orange dots and/or globules	0	72.7
		Yellowish-orange crusts	0	63.6
Çetinarslan, et al. J Dermatol 2020/ Prospective comparative	35/55	Vessel type:
		Dot/glomerular/linear/	51.4/0/2.9/	58.2/7.3/3.6/
		hairpin/red globular ring/undifferentiated	0/14.3/31.4	1.8/0/29.1
		Vessel distribution:	40/25.7/2.9/	3.6/20/47.3/
		Regular/clustered/patchy/undifferentiated	31.4/65.7/0/34.3	29.1/1.8/85.5/12.
		Scale colour:		7
		White/yellow/white + yellow
		Scale distribution pattern:	74.3/11.4/	56.4/41.8/
		Diffuse/patchy	11.4/2.9	1.8/0
		/peripheral/central
		Background colour:
		Light red/DR/yellowish/	48.6/5.7/8.6/	12.7/32.7/16.4/
		yellowish+full red/yellowish + light red	22.9/14.3	36.4/1.8
		Brownish-orange globules	5.7	34.5
		Yellow crusts	8.6	40
		Hemorrhagic crust	25.7	27.3
		Yellow-orange areas	28.6	43.6
Yu, et al. Medicine (Baltimore) 2021/	26/31	Background colour:
Not mentioned		Red/pink	57.7/42.3	12.9/87.1
		Scale colour:
		White/yellow	92.3/50	45.2/61.3
		Morphology of vessels:
		Dots or globular/atypical/hairpin	84.6/7.8/34.6	22.6/93.5/0
		Distribution/arrangement of vessels: Regular/irregular	100/3.8	6.5/93.5
Present study/ Cross-sectional, comparative	39/42	Vessel distribution:
		Focal/regular or diffuse/none	12.8/84.6/2.6	61.9/2.4/35.7
		Background colour:
		DR or pink/yellow to YO/Combination	69.2/0/30.8	0/88.1/11.9
		Scale distribution:
		Patchy/diffuse	12.8/87.2	33.3/66.7
		Scale colour:
		White or white grey/yellowish/both	15.4/5.1/79.5	0/76.2/23.8
		Yellow + white linear lines	56.4	11.9
		Brown/orange-brown dots and globules	0	66.7
		Yellow/yellow-orange crust	7.7	57.1

PP: Palmar/plantar psoriasis; PE: palmar/plantar eczema; DR: dull red; YO: yellow-orange

Table 4.

Predominant dermoscopy findings in PPP and PPE

Dermoscopy characteristic	Palmoplantar psoriasis	Palmoplantar eczema
Background colour	Dull red/pink	Yellow/yellow-brown
Vessel distribution	Regular vessels	Patchy vessels or absence of vessels
Scale colour and distribution	Combination of white/grey-white and yellowish scales diffusely present	Yellow scales (Diffuse>focal)
Additional findings	Yellow-white lines or streaks	Brown/orangish-brown dots or globules Yellow/yellow-orange crust

The limitation of the present study is the inability of the authors to correlate each dermoscopic finding with those seen in the histopathology of the patients. Though the sample size in the present study is larger than the earlier study by Errichetti and and Stinco,[13] and comparable to the study by Çetinarslan et al.,[15] more studies with a larger number of patients are needed to corroborate further the findings observed in the present study.

We conclude that dermoscopy can act as a useful, rapid and easy-to-perform bedside tool in the armamentarium of a dermatologist when faced with hyperkeratotic plaques over the palmoplantar area. A stepwise approach starting with non-polarized, non-contact mode, followed by non-contact polarized mode and then usage of linkage fluid with polarized mode should be employed during the dermoscopic examination of palmoplantar plaques to appreciate the underlying findings better. When diffuse scales are seen with regular vessels over a dull red background without brownish dots and globules, a diagnosis of psoriasis should be favoured. The diagnosis of eczema should be proffered following the presence of yellow scales with focally distributed vessels, brown/orange-brown dots and/or globules and yellow/yellow-orange crust over a yellow/yellow-brown background [Table 4].

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.