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Telltale signs of skin trespassers: Clues to superficial mycosis
How to cite this article: Varsha MG, Shilpa K, Revathi TN, Shanmukhappa AG, Loganathan E. Telltale signs of skin trespassers: Clues to superficial mycosis. Indian J Dermatol Venereol Leprol 2023;89:144-8.
Superficial fungal infections constitute the commonest reason for a dermatologic consultation across India. However, recently they have become a diagnostic challenge due to various reasons. This article highlights certain signs and appearances that may facilitate their diagnosis.
Besnier’s sign/scratch sign/stroke of the nail/coup d’ongle sign
Double-edged Tinea/Ring-within-Ring Appearance
It is an important clinical marker of steroid modified tinea.2 Due to relapsing inflammation, there is incomplete clearance of the fungal elements which clinically presents as parallelly arranged erythematous borders. This creates a double-edged appearance and the annular lesions develop multiple concentric rings spreading centrifugally, appearing like ‘ring within ring’ [Figure 2].3
This appearance also indicates tinea incognito, characterised by the confluence of multiple annular lesions of various sizes across multiple anatomical locations. Additionally, there is loss of central clearing with eczematisation, creating a ‘dumbbell’ appearance [Figure 3].2,3
Ear sign denotes the presence of erythematous scaly papules and plaques over helix, antihelix and retroauricular region, sparing the retroauricular fold, classical of tinea capitis. Notably, identical lesions involving the retroauricular folds indicate seborrheic dermatitis.4 Recently, ‘ear sign’ has also been attributed to the involvement of auricular pinna, suggestive of ipsilateral tinea faciei [Figure 4].3
Egg Crackling Sign
This clinical sign has been described in elderly patients with pityriasis versicolor. On stretching the lesion, the overlying scales break like the crackling of an eggshell.
Salt and Pepper Appearance
Tinea nigra is a superficial fungal infection characterised by asymptomatic brown to black macules and patches over palms and soles. A rare variant has been described which forms the speckled or ‘salt and pepper’ pattern over the palms.5
Zireli’s Sign/Evoked Scale Sign/Stretch Sign
On stretching the lesions of pityriasis versicolor with two fingers at 180° angle, the corneal layer parasitised by Malassezia gets exposed.6 This sign helps to differentiate pityriasis versicolor and other disorders involving dyspigmentation [Figure 5].7
Aurora borealis pattern
On onychoscopy, onycholytic nail plate demonstrates multiple longitudinal lines of varied colours (yellow, brown, white, etc.) similar to the colours of aurora borealis. They represent fungal colonies, subungual debris and invasion, and is most commonly observed in distal and lateral subungual onychomycosis [Figure 6].8
This sign indicates post-treatment cases of tinea capitis. As the endothrix spores are eliminated by antifungals, the corkscrew hair become more fragile and easily breakable. New uninfected hair replaces them, which resemble cigarette ash on dermoscopy.9
It is a trichoscopic feature of tinea capitis. Multiple hyphae fill the hair follicle resulting in cracking and bending of the hair shaft with a marked distal angulation resembling ‘comma’ [Figure 7].10
Contrast Halo Sign
Dermoscopy of pityriasis versicolor reveals increased pigmentation around hypopigmented lesions and identical decreased pigmentation around primary lesions of hyperpigmented variant. This is called ‘Contrast halo sign’ [Figure 8].
Proposed mechanism – In hypopigmented variant, the compensatory melanogenesis occurs due to cytotoxic damage and abnormal melanosomes in the primary lesion, while in hyperpigmented variant, the consumption of melanocytes occurs as a response to the stimulated melanogenesis in the primary lesion due to perivascular inflammation.11
Fish Net/Wire Fence Appearance
It is an easy and quick dermoscopic clue to pityriasis versicolor, useful when scratch sign is clinically negative. It is characterised by fine scales along the normal skin markings against a hypo/hyperpigmented background, simulating a ‘wire fence’/‘fish net’. [Figure 9].12
Morse Code/Bar Code Hair
It is a recent dermoscopic feature reported in tinea capitis and corporis, appearing as subtle interrupted horizontal white bands due to localised fungal invasion.13 These bands are multiple and represent ‘locus minoris resistentiae’ that make the hair easily deformable, translucent and fragile [Figure 10].14
It is a specific dermoscopic feature of tinea corporis. Motheaten scales represent multiple annular lesions with peripheral scaling, coalescing to form larger multicyclic lesion in outward peeling direction [Figure 11].15
Reverse Triangular Pattern
This pattern is described in onychoscopy of onychomycosis. The black reverse triangle forms as wider nail pigmentation occurs at the distal end indicating fungal invasion from that end. The triangular sign is also observed in ungual melanoma and nail matrix nevus in children [Figure 12].16
Ruin appearance is the special dermoscopic term depicting subungual keratosis in onychomycosis. It denotes the indentations of the ventral nail plate which occur due to accumulation of dermal debris in response to fungal invasion. It is classical for total dystrophic onychomycosis [Figure 13].17
Telephone Handle Hair
It is a novel trichoscopic finding in tinea capitis. Due to fungal invasion, the hair shafts become easily deformable, horizontally bent with slightly bulbous appearance on either side resembling a ‘telephone handle’ [Figure 7].18
It is another common trichoscopic feature in tinea capitis. The conidia on hair surface following fungal invasion of hair cuticle bends the paler part of infected hair resulting in its structural weakness and zigzag hair [Figure 7].10
Butter cream frosting appearance
It describes the colony appearance of Trichosporon spp., the causative organism of white piedra. On Sabouraud’s dextrose agar, rapid growth of moist cream-coloured yeast-like colonies resemble ‘butter cream frosting.’19
It is the most common artefact encountered during direct microscopic examination of skin scrapings for fungal elements. KOH dissolves normal epidermal cells forming irregular branching network resembling fungal structures [Figure 14].20
Spaghetti and Meatballs/Banana and Grapes Appearance
On KOH mount examination of scales of pityriasis versicolor, thick-walled spherical yeasts of Malassezia furfur are present in clusters with scattered short septate filaments (2–5 μ wide, 25 μ long) resembling ‘banana and grapes’ or ‘spaghetti and meatballs’. [Figure 16].20
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Conflicts of interest
There are no conflicts of interest.