From the Sea to the Skin: Exploring Dermatological Eponyms Inspired by Aquatic Animals

Introduction The human body and the natural world often find curious parallels, and dermatology is no exception. Many dermatological conditions are named after marine animals due to their distinctive appearances or the historical contexts of their discovery. This article delves into a fascinating collection of dermatological eponyms based on aquatic animal and summarized in table 1.Table 1: Summary of dermatological eponyms related to aquatic animals Caviar tongueCaviar tongue, caused by aging and degeneration of sublingual vein elastic tissue, can also be associated with portal hypertension or superior vena cava syndrome, leading to increased venous pressure in these conditions.[1]Caviar appearance on dermoscopyExogenous ochronosis, linked to hydroquinone, phenol, and antimalarials, involves homogentisic acid accumulation in the dermis. It occurs in high phototypes with three stages: erythema, hyperpigmentation with colloid milia (caviar-like lesions), and papulo-nodular lesions.[2]Crab lousePhthiriasis pubis, commonly known as crab louse infestation, features a squat body with pincer-like claws. This ectoparasite is typically found in the pubic region and causes itching and a sensation of crawling.[3]Crab yawsYaws, a tropical infection caused by Treponema pallidum pertenue, manifests in painful palmoplantar keratoderma in its secondary stage and fissured keratoderma in the tertiary stage. These lesions are reminiscent of wet or dry crab claws, respectively, hence the name “crab yaws.”[4]Fish mouth woundsIn Ehlers-Danlos syndrome, a group of connective tissue disorders, gaping scars on bony prominences resemble fish mouths, often referred to as “fish mouth wounds.”[5]Fish-like skinIchthyosis, derived from the Greek word for fish, involves generalized xerotic and thickened skin with “fish-like” scaling [Figure 1] due to altered epidermal cell kinetics and differentiation.[6]Fish net appearance Direct immunofluorescence in pemphigus vulgaris and pemphigus foliaceus reveals a “fishnet” or “chicken-wire” pattern [Figure 2]. This is due to IgG and C3 autoantibodies against desmoglein 1 and 3 in the epidermis. Dermoscopy of pityriasis versicolor shows fine scaling arranged along normal skin markings against hypopigmented or hyperpigmented skin, giving a “fish net” or “wire fence” appearance.[7] Fish odor syndromeTrimethylaminuria, or fish odor syndrome, is a rare metabolic disorder caused by a deficiency of the enzyme flavin-containing monooxygenase 3, leading to the accumulation of trimethylamine, which produces a strong fish-like odor. The odor’s intensity varies with diet, stress, hormones, and medications.[8]Fish pedicureIt is also called ichthyotherapy, and this biotherapy uses Garra rufa fish to exfoliate the skin [Figure 3]. However, its safety is questioned due to potential infections, emphasizing the need for caution and proper hygiene in such practices.[9]Fish skin graftFish skin grafts, known for accelerating wound healing, disease-free application, and low-cost production, offer a promising alternative to traditional skin grafts, making them increasingly popular in clinical settings.Fish tank granulomaFish tank granuloma, caused by Mycobacterium marinum, results from aquarium exposure. It presents as erythematous papules, nodules, plaques, or verrucous lesions, potentially leading to deeper tissue infections.[10]Fish-tail deformityPsoriatic arthritis can cause splaying of the distal phalanx base due to new bone formation, termed “fish-tail deformity.”Fishman syndromeEncephalocraniocutaneous lipomatosis, or Fishman syndrome, presents with congenital skin, eye, and brain lesions due to dysgenesis of the anterior neural tube and cephalic neural crest.[11]Jellyfish dermatitisJellyfish envenomation causes acute, hemorrhagic vesiculopapular eruptions. Rarely, it leads to type IV allergic hypersensitivity with delayed or recurrent lesions.[12]Lobster claw deformityEctrodactyly-ectodermal dysplasia-clefting syndrome features syndactyly with oligodactyly and median clefts of the hands and feet, creating a “lobster claw” appearance.[13]Ostraceous psoriasisPsoriatic lesions that are characterized by ring-like hyperkeratotic scaly plaques with concave surfaces resembling an oyster shell are typical of ostraceous psoriasis.Oyster shell crustIt is seen in late syphilis. Large plaques with black, brown, or green crusts resembling an oyster shell’s outer layer create a “rupioid” appearance.[14]Rupioid psoriasisRupioid psoriasis is characterized by thick, keratotic, cone-shaped lesions resembling limpet-like scales, a mollusc seen in the sea.Salmon patch Nevus flammeus simplex, or “stork marks,” are birthmarks that fade with pressure and typically disappear in early childhood. Found on the nape, eyelids, or forehead, they resemble the pinkish hue of salmon flesh. In the late stage of syphilis, a dull pink patch appears at the edge of the cornea due to circumcorneal vascularization called a salmon patch. Oil-drop pigmentation, or salmon patch [Figure 4], in psoriasis and psoriatic arthritis, resembles oil on paper, indicating cellular debris and serum under the nail. School of fish appearanceIn chancroid, a sexually transmitted infection caused by Haemophilus ducreyi, Gram-stained smears show Gram-negative coccobacilli in clusters resembling a “school of fish.”Sea anemone appearance Black hairy tongue shows a “sea anemone” appearance on dermoscopy, with elongated papillae displaying a color gradient from base to tip.[15] Onychomatricoma is a rare and benign tumor of the nail matrix but rarely originates from the ventral portion of the proximal nail fold. Under local anesthesia, when the nail plate is avulsed, a matrix villous tumor becomes visible. This tumor presents with a distinctive appearance, resembling a “sea anemone” due to its characteristic digitations.[16] Shagreen patchShagreen, a type of leather with a distinctive raised texture, was originally made from fish skin. A shagreen patch is an irregularly shaped, elevated, soft, and skin-colored area typically found on the lower back [Figure 5]. It consists of excess fibrous tissue and is commonly associated with tuberous sclerosis complex.Snail track ulcersSecondary syphilis can cause coalescing mucous patches in the mouth, forming serpiginous “snail track” ulcers.[17]Starfish keratosisVohwinkel keratoderma, also known as keratoderma hereditaria mutilans, is characterized by diffuse PPK in a honeycombed pattern, pseudoainhum leading to autoamputation, and “starfish-shaped” hyperkeratotic plaques on the hands, feet, elbows, and knees.[18]Tadpole cellsHistopathology of syringoma reveals “tadpole cells,” which are small ducts and epithelial cords lined by two rows of epithelial cells resembling tadpoles.[19]Tadpole seborrheic keratosisA rare linear variant of seborrheic keratosis, tadpole seborrheic keratosis, resembles a “tadpole” or “comet tail.”[20]Toad skinPhrynoderma, a type of follicular hyperkeratosis, is linked to nutritional deficiencies. The term “phrynoderma,” introduced by Nicholls in 1933, describes the skin’s “toad-like” appearance in malnourished individuals. This dermatosis can result from deficiencies in vitamins A, B complex, C, and E.[21]Frog spawn appearance Lymphangioma circumscriptum, a benign lymphatic malformation, presents as grouped, clear, fluid-filled, or hemorrhagic vesicles resembling frog spawn [Figure 6].[22] Dermoscopy of verruca vulgaris reveals a “frog spawn” appearance. This characteristic pattern is marked by groups of compactly packed papillae, each featuring a central red dot surrounded by a whitish halo [Figure 7].[23] Figure 1: Fish-like scales on both legs in a case of ichthyosis vulgarisFigure 2: Direct immunofluorescence showing fishnet appearance in a case of pemphigus vulgarisFigure 3: Fish pedicureFigure 4: Salmon patch or oil drop sign in a case of nail psoriasisFigure 5: Multiple small shagreen (sharkskin) patches on the lower back in a case of tuberous sclerosisFigure 6: Cluster of small blisters filled with lymph fluid, with few hemorrhagic blisters, resembling frogspawn suggestive of lymphangioma circumscriptumFigure 7: Polarized contact dermoscopy (DL4 10X) of verruca vulgaris on the palm showing frog spawn appearance (red circle)In conclusion, by drawing connections between the sea and our skin, these aquatic-inspired dermatological eponyms not only provide vivid descriptions but also aid in the diagnosis and understanding of various skin conditions. They highlight the intricate beauty and complexity of dermatology, making the study of skin disorders both fascinating and informative. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.