Lepidoptera Lexicon: Metaphorical Descriptors in Dermatology

Introduction In the field of dermatology, various clinical and dermoscopic signs, conditions, and phenomena are often described using metaphoric language, particularly involving the terms “butterfly” and “moth.” These descriptive terms not only enhance the visual understanding of clinical presentations but also provide insight into the underlying pathophysiology of different dermatological disorders. The butterfly and moth metaphors have been applied to various conditions, each with distinct clinical and diagnostic significance. From “butterfly rash” seen in lupus erythematosus to “moth-eaten” alopecia in syphilis, these terms illustrate the diversity of skin manifestations and their respective interpretations in clinical practice and are summarized in Table 1.Table 1: Summary of Lepidoptera conditions and named signsButterfly rash A butterfly rash or malar rash is seen as raised or flat, fixed erythema on the malar area, which is usually non-pruritic and scaly, sparing the nasolabial fold [Figure 1]. It is a highly specific but less sensitive clinical finding seen in acute cutaneous lupus erythematosus. This pattern of rash can also be seen in dermatomyositis, papulopustular rosacea, seborrheic dermatitis, and erysipelas.[1]Figure 1: A 24-year-old female with systemic lupus erythematosus presenting with a butterfly or malar rashButterfly sign a. Prurigo: It represents the normal or apparently normal appearance of the skin on mid-back in patients with intense pruritus due to their inability to scratch this site [Figure 2]. Telfer Reynolds first described it in primary biliary cirrhosis. Still, it can be seen in any intensely itchy generalized pruritic conditions like prurigo nodularis, atopic dermatitis, acne excoriee, pediculosis corporis, and other hepatobiliary disorders. In many cases, it can present in varying shapes rather than the classical butterfly shape and is therefore collectively called a “Butterfly sign sine butterfly.”[2] b. Scabies: In scabies, a dermoscopic sign known as the “butterfly sign” may be seen just below the delta glider sign. It appears as a butterfly-shaped reddish area, representing the gut of the mite filled with blood. This finding is thought to be a marker of the mite’s adaptation, potentially indicating emerging resistance to permethrin.[3] Figure 2: A 56-year-old male with prurigo simplex displaying the butterfly sign on the upper backButterfly disease Epidermolysis bullosa is commonly referred to as butterfly disease due to the extreme fragility of the skin seen in this condition, which is similar to the delicate wings of a butterfly. The affected individuals characteristically present with extremely fragile skin with recurrent blister formation at sites of minor mechanical friction or trauma. The affected children are called butterfly “children.”[4] Butterfly effect It refers to the fact that a very small change in one state is associated with a larger difference in the later state. This has been attributed to acne and rosacea in dermatology. Though these are the conditions primarily affecting the skin, the impact of these diseases is comparable to systemic diseases due to their cosmetically unpleasant nature, resulting in fear, anger, depression, and stigmatization among patients.[5] Butterfly pox Erythema infectiosum is otherwise called butterfly pox. It can present as an erythematous rash on the cheeks with circumoral pallor resembling the wings of a butterfly.[6] Chrysalis baby Chrysalis babies are collodion babies with intermediate clinical features.[7] Chrysalis structure They are dermoscopically appreciable shiny, white, orthogonally oriented linear streaks that correspond to dermal fibroplasia [Figure 3]. The birefringence properties of collagen result in a backscatter of polarized light, making collagen more apparent through a polarized dermoscope. They can be seen in conditions with increased or altered collagen, like melanoma, spitz nevi, basal cell carcinoma, dermatofibroma, scars, and porokeratosis.[8]Figure 3: Dermoscopy (DL4 10×) of basal cell carcinoma, highlighting the chrysalis structure (red arrows)Caterpillar dermatitis Lepidopterism, or erucism, involves cutaneous reactions from caterpillar setae and spines, ranging from localized stinging, papular dermatitis, and urticarial rash [Figure 4] to severe conditions like anaphylaxis and hemorrhagic diathesis. Other symptoms include dendrolimiasis, arthropathy, and pararamose, along with ocular ophthalmia nodosa and oral dysphagia, erythema, and pruritus.[9]Figure 4: Caterpillar dermatitis on the neck, manifesting as papular urticaria and dermatitisCaterpillar bodies These are eosinophilic bodies in the epidermis that are elongated and segmented, forming a part of the blister roof in porphyria cutanea tarda. They are seen as linearly arranged periodic acid-Schiff (PAS)-positive globules in the roof of the blister. They are considered to be highly specific for porphyria cutanea tarda but less sensitive as clusters of caterpillar body-like structures can be seen in blistering disorders like bullous pemphigoid and epidermolysis bullosa.[10] Moth-eaten alopecia They are clinically seen as multiple patchy areas of hair loss that are non-scarring in nature [Figure 5]. It is pathognomic of secondary syphilis. However, mimics of moth-eaten alopecia can be seen in alopecia areata, non-inflammatory tinea capitis, and trichotillomania. Syphilitic alopecia can present in varying patterns, such as moth-eating patterns, diffuse hair loss patterns, or both.[11]Figure 5: Moth-eaten alopecia on the scalp in a case of secondary syphilisMoth-eaten scales It is a dermoscopic finding specific to tinea corporis. It is seen as annular lesions with peripheral scaling in an outward peeling direction [Figure 6].[12]Figure 6: Dermoscopy (DL4 10×) of tinea corporis, showing moth-eaten scales at the periphery of the lesionMoth-eaten borders It is a dermoscopic finding that has been noted in cases of seborrheic keratosis. It is seen as sharply demarcated indentations at the borders.[13] The moth-eaten appearance of the iris It occurs as sequelae secondary to resolved chronic anterior uveitis that occurs in Hansen’s disease. The moth-eaten appearance of the iris can also be seen in Fuchs heterochromic iridocyclitis.[14] The moth-eaten appearance of skin a. Pseudomonas pyoderma It is a superficial bacterial infection mostly seen as a secondary bacterial infection in tinea pedis, eczematous eruption, infection of bed sore, burns, and graft site. The cutaneous lesion produced by them has an irregular border that is macerated and eroded, giving a characteristic moth-eaten appearance.[15] b. Atrophoderma of Pasini and Pierini It is considered as a localized variant of morphea. The cutaneous lesions of the atrophoderma of Pasini and Pierini can coalesce over time due to a lack of sclerosis, resulting in a moth-eaten appearance.[16] In conclusion, the use of metaphorical language, such as “butterfly” and “moth,” in dermatology highlights the unique and often vivid presentations of various skin conditions. These terms serve as valuable diagnostic tools, helping clinicians recognize and differentiate between diseases based on their characteristic appearances. Understanding these metaphors not only aids in clinical diagnosis but also enriches the descriptive language of dermatology, fostering a deeper appreciation of the intricate patterns and presentations observed in skin pathology. As dermatology continues to evolve, these metaphorical descriptors remain integral to both the communication and understanding of complex dermatological phenomena. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patients have given their consent for their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest. Use of artificial intelligence (AI) The preparation of this manuscript was carried out entirely by the author without the use of artificial intelligence technologies.