The word “sign” refers to important physical finding or observation made by the physician when examining the patient. Dermatologic diagnosis relies on the careful observation and documentation of signs, which can be highly pathognomonic for a certain conditions. Most of the signs appear either de novo or have to be elicited by the physician. Until date, there are only two papers describing the signs observed in dermatologic disorders.[^{1, 2}] We have reviewed these papers and updated the newly described signs in the present paper. We have also incorporated the signs recently by Indian workers in the field of dermatology. The historical and pathophysiological aspects of the “signs” mentioned in this review paper are beyond the scope.

This is seen in Albright's hereditary osteodystrophy in which there is presence of a dimple over the knuckle of the typically affected fourth metacarpal and can be enhanced by clenching of the fist.[^{3, 4}]

It is seen in keratosis pilaris in which individual follicles show a long strand of keratin glinting when examined in tangentially incident light.[⁵]

Gustav Asboe Hansen first described it in 1960, when he demonstrated enlargement of bulla by applying finger pressure to small, intact, and tense bulla in patients with pemphigus and bullous pemphigoid.[⁶] In the traditional bulla spread sign, pressure is applied to the blister from one side, whereas in eliciting Asboe-Hansen sign pressure is applied at the center of the blister and perpendicular to the surface due to smaller size of the lesion.

It is a celebrated sign of dermatology named after Heinrich Auspitz, described in psoriasis, where there is pinpoint bleeding on removal of scales from the lesions of psoriasis. The test by which Auspitz sign is elicited is called as Grattage test. Other dermatoses where Auspitz sign can be positive is Darier's disease and actinic keratosis.[⁷]

It is ridging and tightening of the skin of the neck on extending the head with a visible and palpable tight band over platysma in the hyperextended neck.[^{8, 9}]

It is to be elicited in cases of arterio-venous fistula where there is slowing of the heart rate in response to (manual) compression.[¹⁰]

The bites of bed bugs (Cimex lectularius) usually follow a linear pathway in a group of three to five blood meals and are often referred to as “Breakfast, lunch, and dinner” or “Breakfast, lunch, and supper” sign.[¹¹]

This is a sign to be elicited in case of secondary syphilis and cutaneous vasculitis, where there is deep dermal tenderness on pressing the lesion (e.g., papular lesions of syphilis) with a pinhead.[¹²]

This refers to sparing of the mid scapular region in patients having prurigo nodularis with neurodermatitis as they are unable to reach the region for scratching.[¹³]

In type 1 neurofibromatosis (Von-Recklinghausen's disease), neurofibromas can be invaginated with the tip of index finger back into the subcutis and again reappear after release of pressure.[¹⁴] Other condition where one can find positive buttonhole sign are anetoderma and dermatofibroma.

When the adherent scale is removed from the lesions of discoid lupus erythematosus, the undersurface of the scale shows horny plugs that have occupied patulous hair follicles. This sign is also seen in seborrheic dermatitis.[⁷]

In about eighty percent of cases of Chagas’ disease (American trypanosomiasis), conjunctiva is the portal of entry for Trypanosoma Cruzi. Unilateral swelling of eyelids and orbit after conjunctival inoculation is called as eye-sign or Chagas–Mazza–Romaña's sign or Romaña's sign.[¹⁵]

Papules seen around the nail fold in multicentric reticulohistiocytosis are called as coral bead sign.[¹⁶]

It was first described by Shuster in cases of alopecia areata in 1984. Coudability sign is normal-looking hairs tapered at the proximal end in the perilesional hair-bearing scalp and can easily be made to kink when bent or pushed inward.[¹⁷]

Axillary freckling seen in type I neurofibromatosis is known as Crowe's sign.[¹⁸] (See also Patrick Yesudian sign)

Periumbilical ecchymosis in cases of acute hemorrhagic pancreatitis and ruptured ectopic pregnancy is termed Cullen's sign. Similar changes in the flank is called as Grey-Turner sign.[¹⁹]

It was classically described in Papulo-erythroderma of Ofuji, wherein there is flat-topped red papules that become generalized erythrodermic plaques without the involvement of abdominal skin folds.[²⁰]

Rubbing a lesion of mastocytoma causes urtication, flare, swelling and sometimes blister formation due to release of histamine. In contrast, pseudo-Darer's sign is seen in smooth muscle hamartoma where there is increase in induration and piloerection after firm stroking.[²¹] Other conditions where one could find positive Darier's sign are leukemia cutis, juvenile xanthogranuloma, and Langerhans cell histiocytosis.

Squeezing the skin adjacent to a dermatofibroma causes a dimpled appearance on its surface, also termed a positive “pinch sign” or “dimple sign,”[²²]

It is described in relation to syphilitic chancre on the coronal border of the prepucial skin in an uncircumscribed male, whereupon on retracting the foreskin the entire ulcer flips out all at once because it is too hard to bend due to underlying button like induration.[²³]

• (i)  The presence of sharply demarcated alternating bands of normally pigmented and hypopigmented zone of hair indicating episodes of normal nutrition and intermittent malnutrition respectively, seen in kwashiorkor- or marasmus-type malnutrition.[²⁴]
• (ii)  It is a histopathological sign described in actinic keratosis, in which the basal layer is more basophilic than normal owing to crowding of atypical keratinocytes. Hyperkeratosis and parakerotosis are present, the latter overlying the abnormal cells in the epidermis. Owing to sparing of the epithelium of acrosyringia and acrotrichia, orthokeratosis appears at the ostea of these structures, giving rise to a characteristic pattern of alternating ortho- and parakeratosis, often referred to as the “flag” sign.[²⁵]

Seen in 20% of rubella patients, where there is an enanthem of dull-red macules or petechiae confined to the soft palate during the prodromal period or on the first day of the rash.[²⁶] Can also be seen in infectious mononucleosis.

Diagonal crease in the earlobes of adults has been associated with an increased risk for atherosclerotic heart disease.[²⁷]

Friar tuck was a companion of Robin Hood in the legendary stories who had alopecia of the vertex with sparing of occipital region. This is described in relation to trichotillomania, where patient plucks his own hair either in a wave like pattern across the scalp or centrifugally from a single starting point. Hairs over the occipital area are mostly spared in trichotillomania and is referred as Friar Tuck sign.[²⁸]

It is the ability of patients of Ehlers-Danlos syndrome to touch the tip of the nose with the tip of their tongue.[²⁹]

It is a characteristic finding in dermatomyositis typified by scaly erythematous eruption seen on the dorsa of hands, metacarpophalangeal joints, and proximal interphalangeal joints.[³⁰]

It is classically described in eosinophilic fasciitis (Shulman's syndrome) where there is linear groove or indentation along the superficial veins of the medial aspect of the upper extremity.[³¹]

Another Groove sign has been described in relation to chlamydial infection, i.e., lymphogranuloma venereum (LGV) called as Groove sign of Greenblatt and is considered pathognomonic for LGV. Enlargement of both inguinal and femoral group of lymph nodes separated by Poupart's ligament produces a groove known as the “Groove sign of Greenblatt.”[³²]

This refers to the dark triangular biting apparatus of Sarcoptes scabiei seen at the end of the subcorneal tunnel.[³³]

It is a marker of cranial dysraphism, including encephalocele, meningocele, and heterotropic brain tissue. Ectopic neural tissue in the occipital and parietal areas takes the form of smooth dome-shaped hairless nodules and sometimes a collar of hypertrichosis surrounds them, this is called as hair-collar sign.[³⁴]

It is a characteristic histopathological finding seen in prurigo nodularis, where there is a presence of thick compact orthohyperkeratosis; the hairy palm sign (folliculosebaceous units seen with a thick and compact cornified layer, seems like that biopsy has been taken from palm, i.e., volar skin but contains pilosebaceous unit).[³⁵]

This sign has been described in relation to trichotillomania, wherein there is vertically oriented split of hair shafts and proteinaceous material and erythrocytes are present in the split resembling a hamburger within a bun.[³⁶]

It is seen in patients with pityriasis rosea. When the skin is stretched across the long axis of the herald patch, the scale is noted to be finer, lighter, and attached at one end, which tends to fold across the line of stretch.[³⁷]

It is defined as loss of lateral one third of eye-brows (superciliary madarosis). It is seen in leprosy, myxedema, follicular mucinosis, atopic dermatitis, trichotillomania, ectodermal dysplasia, discoid lupus erythematosus, alopecia areata, syphilis, ulerythema ophryogenes, systemic sclerosis, HIV infection, and hypothyroidism.[³⁸]

It refers enlargement of the sternal end of the (right) clavicle, frequently observed in patients with late congenital syphilis.[³⁹]

Literally, holster means an extra pocket made from various materials to hold something where it can quickly be taken out for use (e.g., Gun holster). Confluent macular violaceous erythema present on the lateral side of hip and thighs is called as “Holster sign” corresponding to the site of hanging a holster.[⁴⁰]

• (i)  Melanonychia with pigmentation of proximal nail fold seen in subungual melanoma.[⁴¹]
• (ii)  Presence of papulo-vesicular lesions on the tip of nose indicates involvement of cornea as both are supplied by nasociliary nerve, a branch of trigeminal nerve.[⁴²]
• (iii)  Micro-Hutchinson's sign: pigmentation of the periungual tissues that could not be seen with the naked eye and can be visualized by dermoscopy.[⁴³] Micro-Hutchinson's sign is a highly characteristic dermoscopic feature of early nail apparatus melanom a, although the sensitivity is not high.

Hypopyon sign describes the presence of small, discrete, vesicles either flaccid or tense that become secondarily infected and pus accumulates in the lower half of the pustule. It is a clinical sign seen in pyodermas and secondarily infected vesicobullous disorders (e. g., pemphigus, bullous pemphigoid, and linear IgA dermatosis), where there is a transverse fluid level comprising of purulent material at the bottom when the patient is in a standing position and is called hypopyon sign.[⁴⁴]

Inability to retract the lower eye-lid in patients of progressive systemic sclerosis due to underlying sclerosis is called Ingram's sign.[⁴⁵]

Pigmentation of the eyelids seen in hyperthyroidism is called as Jellinek's sign.[⁴⁶]

Inability to pinch or pick up a fold of skin at the base of the second toe because of its thickness is seen in chronic lymphedema.[⁴⁷]

First described by Edmund Leser and Ulysse Trelat, characterized by sudden eruption of numerous seborrhoeic keratosis, usually associated with pruritus and is considered as a marker of internal malignancy.[⁴⁸]

Exact localization of tenderness with the help of pin head in glomus tumor is called as Love's sign.[⁴⁹]

Patient having delusions of parasitosis (acarophobia, entomophobia) collects skin debris with mistaken belief that such collected material contains alleged parasite in a matchbox, tissue paper, or small container. This whole exercise executed by the patient is referred to as “matchbox sign.”[⁵⁰]

It is described in Fordyce's disease, characterized by presence of ectopically located sebaceous glands on the lips, oral mucosa and less commonly on gums. Prominent lip involvement can result in a lipstick like mark left on the rim of a glass mug after consuming a hot beverage (Meffert's sign).[⁵¹]

Erysipelas and cellulitis have traditionally been defined as acute inflammatory processes of infectious origin that primarily affect the dermis (in the case of erysipelas) or deeper dermis and subcutaneous tissue in cellulitis.

It is a sign used to distinguish between erysipelas and cellulitis of the facial region, where there is involvement of ear in erysipelas and sparing in cellulitis, as there is no deeper dermal tissue and subcutaneous fat.[⁵²]

It is seen in Raynaud's phenomenon associated with systemic sclerosis. This sign refers to disappearance of the peaked contour on fingerpads and replacement with a hemisphere-like fingertip contour especially on ring fingers.[⁵³]

Follicular hairy hyperkeratosis (horny follicular spicules) commonly located on the face which shows compact follicle bound hyperkeratosis is a rare but typical clinical finding in multiple myeloma and is termed as Nazzaro's sign.[⁵⁴]

This sign is named after the Russian dermatologist Piotr Vasiliyevich Nikolskiy who described it in 1894. It is a popular and respected sign in dermatology, which refers to easy peeling of skin on applying tangential pressure over a bony prominence and classically seen in pemphigus, toxic epidermal necrolysis, and staphylococcal scalded skin syndrome. Nikolskiy's sign can also be elicited in the oral cavity with the help of cotton-tipped applicator.[⁶]

It is seen in exfoliative dermatitis in which there is complete absence of erythema and scaling of the nose and perinasal areas.[^{55, 56}] It is hypothesized that sparing of nose in exfoliative dermatitis could be due to greater sun-exposure of nose or it could be explained by the mechanism of island of normal skin.

Blue black pigmentation in the sclera near insertion of rectus muscle in patients who have Alkaptonuria (Endogenous ochronosis).[⁵⁷]

Linear petechial eruption in the skin folds especially on the ante-cubital fossa and axillary fold seen in streptococcal scarlet fever is called Pastia's sign.[⁵⁸]

Palmar melanotic macules (palmar freckling) seen in type 1 neurofibromatosis was first reported by Patrick Yesudian and hence the name.[⁵⁹]

Acquired hypertrichosis of eyelashes due to Kala-azar is called as Pitaluga's sign.[⁶⁰]

It is described in relation to diabetic cheiroarthropathy, wherein the patient is requested to bring both the palmar surface of the hands together as at prayer. Prayer sign is said to be positive when patient is unable to bring both the palmar surface together completely and it indicates limited joint mobility. Limited joint mobility is secondary to nonenzymatic glycosylation of collagen and its deposition in the small joints of the hand.[⁶¹]

It is a histopathological finding where there is appearance of a small vessel protruding into an abnormal vascular space has been termed “promontory sign.” It has been described in Kaposi sarcoma, patch and plaque stage of angiosarcoma, and also in a single case of reactive benign vascular proliferation.[⁶²–⁶⁴]

In young women and girls having from vitiligo the original white color of vitiligo macules turns to red-pink during menstruation and after the menstruation, it turns to the original colour.[⁶⁵]

It is seen in nail lichen planus, in which the nail splits and elevates longitudinally with downward angle of lateral nail edge.[⁶⁶]

The most common cutaneous manifestation of neonatal lupus erythematosus is erythematous, slightly scaly eruption on the face and periorbital skin (raccoon sign/owl-eye/eye mask). Periorbital hemorrhage due to laxity of blood vessels seen after proctoscopic examination (postproctoscopic periorbital Purpura) in patients having systemic amyloidosis is also called as Raccoon eyes/sign/panda sign.[⁶⁷–⁶⁹]

Namaskar’ is the typical Indian way of greeting people, where the forearms are folded in front of the chest and the palms are closely approximated together. In patients with hyperextensible joints as seen in Ehler Danlos syndrome, they are able to fold their forearms at the back and oppose their palms to say “Namaskar,” demonstrating the hyper extensible joints.[⁷⁰]

It refers to the thick indurated inflammatory cord like structure that extends from the lateral trunk to the axillae and said to be a classical finding of interstitial granulomatous dermatitis (Ackerman's syndrome) with arthritis.[⁷¹]

Crusted callosity on the knuckles of dominant hand due to repeated self-induced vomiting in patients of bulimia.[^{72, 73}]

In dermatophytosis, fungi are present in the horny layer between two zones of cornified cells, the upper being orthokeratotic and lower consisting partially parakeratotic cells.[⁷⁴]

This sign is to be elicited in patients having pityriasis versicolor, wherein the barely perceptible scales are made to stand out by scratching the lesion with fingernail.[⁷]

Confluent macular violaceous erythema on the posterior neck and shoulders in patients of dermatomyositis is called Shawl sign.[⁷⁵]

Dystrophic and ragged cuticle seen in dermatomyositis is called as Samitz sign.[⁷⁶]

Scarring of the concha due to lesions of discoid lupus erythematosus is called as Shuster's sign and it can be present in 30% of the cases.[⁷⁷]

Stafne's sign is seen in progressive systemic sclerosis. Widening of the periodontal ligament space secondary to increase in the collagen synthesis and increase in the bulk of the ligament, this is accommodated at the expense of alveolar bone, thus causing an increase in the width of the periodontal ligament space.[⁷⁸]

In patients of Marfan syndrome, the thumbs protrude from the clenched fist beyond the ulnar border of hand.[²⁹] (See also Umbilical sign and wrist sign).

Linear aggregation of neoplastic lymphocytes along the dermal–epidermal junction seen in histopathology of mycosis fungoides.[⁷⁹]

In 1998, Grob and Bonerandi introduced the “ugly duckling” concept to demonstrate that nevi in the same individual tend to resemble one another and that atypical mole often deviates from the individual's nevus pattern. In other words, nevus that does not resemble other nevi is more likely to be suspicious of melanoma.[⁸⁰]

Umbilical sign is seen in Marfan syndrome. It is the unusual ability to touch the umbilicus with the right hand, crossing the back, and approaching from the left side, indicating increased length of upper extremity.[²⁹]

Confluent macular violaceous erythema on the anterior neck and chest in patients of dermatomyositis is called “V” sign.[⁷⁵]

It is descriptive term for the morphologic feature of Old World cutaneous leishmaniasis. The lesion starts as a small nontender papule, which enlarges in size and ulcerates in the centre. The border of the crusted ulcer often has an erythematous rim and is called as “Volcano sign.”.[⁸¹]

In ulnar nerve paralysis due to leprosy, the little finger assumes the position of constant abduction secondary to paralysis of adductor digiti minimi and is considered the earliest sign of ulnar nerve affection.[⁸²]

Wimberger's sign is the presence of bilateral, symmetrical, and well-defined metaphyseal defects on the medial surface of upper tibia, can result in pseudoparalysis, and is considered pathognomonic of congenital syphilis.[⁸³]

It is seen in early stages of African trypanosomiasis caused by Trypanosoma brucei rhodensiense and Trypanosoma brucei gambiense known Sleeping sickness. Winterbottom's sign is enlargement of lymph nodes in the posterior cervical chain.[⁸⁴]

The distal phalange of the first and fifth fingers of the hand overlaps when wrapped around the opposite wrist seen in patients having Marfan syndrome.[²⁹]