Clinical Dermatology Review

ORIGINAL ARTICLE
Year
: 2020  |  Volume : 4  |  Issue : 2  |  Page : 136--140

Dermoscopic differentiation of pustular psoriasis and tinea incognito


Balachandra S Ankad1, Apoorva S Reshme1, Balakrishna P Nikam2, Nicholas D Drago1,  
1 Department of Dermatology, S Nijalingappa Medical College, Bagalkot, Karnataka, India
2 Department of Dermatology, Krishna Institute of Medical Sciences (Deemed to be University), Karad, Maharashtra, India

Correspondence Address:
Balachandra S Ankad
Department of Dermatology, S. Nijalingappa Medical College, Nava Nagar, Bagalkot - 587 102, Karnataka
India

Abstract

Introduction: Dermoscopy is a rapid diagnostic method in many inflammatory dermatoses which are diagnosed accurately by dermoscopy. Clinically, pustular psoriasis (PP) and tinea incognito (TI) look similar, and sometimes, TI is an invader into PP. Hence, it is important to differentiate each to manage them properly. Thus, a tool to distinguish both TI and PP is necessary for the correct diagnosis and management. Dermoscopy of PP is well-documented but not in TI. Here, we describe the dermoscopic differentiation of TI from PP with histopathological correlation. Materials and Methods: This was a cross-sectional study. Cases of PP and TI were included. DermLite 3 was employed. Potassium hydroxide (10%) mount and histopathological examination were done to confirm the diagnosis. Statistical analysis was done using “z” test. Results: A total of 20 TI and ten PP patients were in the study. Micropustules and scales were seen in all (100%) patients of PP and TI. Brown and black globules and hair changes were seen only in TI (100%), not in PP (0.0%). Red dots were observed in all PP patients (100%), not in TI (0.0%). Erythematous background in PP (100%) and in TI (70%) was statistically significant with P < 0.001. Conclusion: Dermoscopy is an in vivo tool to visualize the deeper structures of the skin. It demonstrates characteristic and different patterns in PP and TI as well, thus aiding in the differentiation of both the conditions. It would help treating physician to manage correctly and avoid unnecessary delay in the accurate diagnosis and treatment.



How to cite this article:
Ankad BS, Reshme AS, Nikam BP, Drago ND. Dermoscopic differentiation of pustular psoriasis and tinea incognito.Clin Dermatol Rev 2020;4:136-140


How to cite this URL:
Ankad BS, Reshme AS, Nikam BP, Drago ND. Dermoscopic differentiation of pustular psoriasis and tinea incognito. Clin Dermatol Rev [serial online] 2020 [cited 2020 Oct 21 ];4:136-140
Available from: https://www.cdriadvlkn.org/text.asp?2020/4/2/136/292465


Full Text



 Introduction



Dermoscopy is a rapid diagnostic method aiding in the appreciation of skin structures. Many inflammatory dermatoses are diagnosed accurately by dermoscopy. Its value in the diagnosis of psoriasis and its variants is well established.[1] Pustular psoriasis (PP) manifests as superficial pustules with an intense erythematous background, and dermoscopy of PP shows red dots and white scales on erythematous background.[2]

Tinea incognito (TI) is a term used to describe a tinea infection modified by topical steroids. Clinically, it presents as erythematous patches with pustules at the border.[3] Dermoscopy of dermatophytosis[4],[5] or TI[6] is not studied much except for the few case reports. It delays the diagnosis and treatment as well. Hence, accurate diagnosis of TI is very important due to its modified morphology. Sometimes, fungus invades secondarily into many inflammatory dermatoses doubling the trouble for treating physician. Diagnosis of both TI and PP, which look alike clinically, highly relies on invasive techniques such as potassium hydroxide preparation and skin biopsy. Thus, a tool to distinguish both TI and PP is necessary for the correct diagnosis and management. Here, we describe the dermoscopic differentiation of TI from PP with histopathological correlation of dermoscopic patterns of both.

 Materials and Methods



This study was a cross-sectional study conducted in the Department of Dermatology in S Nijalingappa Medical College, Bagalkot. Clinically suspected cases of PP and TI were included. Demographic data of patients were noted and tabulated. Dermoscopic examination was done using DermLite 3. Ultrasound gel was employed as interface medium. One of the authors (BSA) analyzed the dermoscopic patterns. Sony camera was used to click and save the images. Potassium hydroxide (10%) mount was done to observe the fungal hyphae under microscopy. Histopathological examination was done to confirm the diagnosis. Data were collected, and statistical analysis was done using “z” test.

 Results



A total of 20 TI (12 males and 8 females) and ten PP (7 females and 3 males) patients were in the study. In PP group, median duration of lesions was 20 days, and age of the patient ranged from 35 to 50 years. The mean age of patients in TI group was 29; range from 10 years to 48 years. Duration of lesions was from 3 months to 9 months. Dermoscopy of PP [Figure 1] and [Figure 2] and TI [Figure 3], [Figure 4], [Figure 5] are summarized in [Table 1]. There was no difference in the morphology of micropustules in PP and TI, which appeared as roundish white globules. Distribution of micropustules was nonfollicular in PP, whereas it was both follicular and nonfollicular in TI. Erythematous background was seen in both PP and TI although no specific vascular pattern was noted in TI. White superficial scales were seen at perifollicular and interfollicular areas in TI. Hair changes in TI [Figure 3], [Figure 4], [Figure 5] included broken hairs, black dots, and translucent hairs. Frequency of each hair changes was not calculated. Histopathological [Figure 6] correlation of dermoscopic patterns is depicted in [Table 2].{Figure 1}{Figure 2}{Figure 3}{Figure 4}{Figure 5}{Table 1}{Figure 6}{Table 2}

 Discussion



Dermoscopy has become a popular diagnostic tool in general dermatology practice in the recent past. Its role is being explored and established in inflammatory and infective dermatoses. However, very little is explained about dermoscopy of PP and TI in the literature. Diagnosis of PP and TI is essentially clinical. Conversely, atypical presentations and morphology modified by topical application pose a diagnostic difficulty. The quantum of confusion doubles if fungus secondarily invades the existing dermatoses such as eczema or psoriasis. Hence, we need to have a quick and noninvasive method to make a diagnosis to start the therapy.

In this study, PP showed regular red dots and micropustules on the erythematous background. Bright white superficial scales were seen arranged diffusely over entire lesion. Distribution of micropustules was nonfollicular in position. This is in accordance with the previous reports of dermoscopy in PP.[2] Thus, regular red dots, micropustules on erythematous background are characteristics of PP.

Dermoscopy of TI showed micropustules and white scales on erythematous background. Brown dots or globules and black globules were noted that represent empty hair follicle and serous discharge and melanin in the epidermis, respectively. We propose that brown globules suggest empty follicles. It should be noted that empty hair follicle looks white under dermoscopy. Conversely, brownish discoloration of these empty follicles without halo in TI can be explained by the fact that fungal invasion into the hair complicates into hair fall with follicular and perifollicular deposition of melanin due to inflammation. Hence, in TI, empty hair follicle appears brown rather than white. Intense itching in TI leads to excoriation, oozing, and inflammation. This results in postinflammatory hyperpigmentation. This is the possible hypothesis that produces black globules in TI. We believe that these two dermoscopic patterns are characteristics of TI, and their presence should make physician to dismiss the diagnosis of PP.

Brown dots or globules are also described in dermoscopy of tinea corporis as brown globules with halo.[4] However, authors did not mention the histopathological basis for the same. We did not observe halo around brown globules. Thus, we feel these are not specific to TI. Furthermore, they were not observed in PP. This is probably due to the skin color.

Previously, dermoscopic patterns in TI were noted by Piccolo et al. that included black dots with halo, micropustules, and erythema without specific vascular pattern.[6] It is important to know that black dot is related to hair and should not be confused with black globules which result from itching and inflammation. In this study, similar dermoscopic features were observed, except for the translucent and broken hairs. Black dots represent the residual hair shaft at the skin surface level and should not be distracted with black dot of melanin pigmentation. However, halo around black dot is not noted, and this disparity probably is again due to the skin color. It should be remembered that hair changes are due to invasion of hairs by the fungus. Broken hairs are the hairs that are broken at certain levels due to defective shafts. Translucent hairs are the vellus hairs which lose their pigmentation due to heavy colonization by the dermatophyte. It is important to know that the presence of translucent hair is an indication to start systemic antifungal therapy. Translucent hairs can also be seen in tinea corporis.[4] Thus, these hairs are not definitive of TI.

White superficial scales are noted in both PP and TI. However, their distribution was different and gave clue to the diagnosis. In TI, scales are concentrated around hair follicles, whereas in PP, they were arranged diffusely over the lesions.

Background color in dermoscopy plays a significant role in the diagnosis of many inflammatory dermatoses. Background color in both PP and TI was erythematous with lesser frequency in TI (70%) as compared to PP (100%). This was statistically significant with P < 0.001. This ensures and reinforces that in inflammatory conditions, it is prudent to give attention to the background color of the lesions.

One of PP [Figure 7] patients showed the dermoscopic features of TI at the periphery of the lesions that included brown dots or globules and black globules [Figure 8] on the erythematous background with regular red dots [Figure 9]. This signifies the importance of dermoscopy in the recognition of dermatophytic infection invading secondarily into the common dermatoses such as eczema and psoriasis.{Figure 7}{Figure 8}{Figure 9}

Hence, dermoscopy shows characteristic patterns in TI such as follicular micropustules, brown dots, black globules, translucent hairs, broken hairs, and black dots which are not observed in PP. Small sample size and lack of culture study are the limitations of this study.

 Conclusion



Dermoscopy is anin vivo tool to visualize the deeper structures of the skin. It demonstrates characteristic and different patterns in PP and TI as well, thus aiding in the differentiation of both the conditions. It would help treating physician to manage correctly and avoid unnecessary delays in the accurate diagnosis and treatment.

Acknowledgment

We would like to thank Dr. Manjula R for her assistance in statistical analysis.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

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2Lallas A, Errichetti E. Papulosquamous disorders. In: Lallas A, Errichetti E, Ioannides D. editors. Dermoscopy in General Dermatology. Boca Raton: CRC Press (Taylor and Francis group); 2019. p. 2-46.
3Solomon BA, Glass AT, Rabbin PE. Tinea incognito and “over-the-counter” potent topical steroids. Cutis 1996;58:295-6.
4Knöpfel N, del Pozo LJ, Escudero Mdel M, Martín-Santiago A. Dermoscopic visualization of vellus hair involvement in tinea corporis: A criterion for systemic antifungal therapy? Pediatr Dermatol 2015;32:e226-7.
5Gómez-Moyano E, Crespo Erchiga V, Martínez Pilar L, Martínez García S, Martín González T, Godoy Diaz DJ, et al. Using dermoscopy to detect tinea of vellus hair. Br J Dermatol 2016;174:636-8.
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