Symptoms of pterygium include persistent redness, inflammation, foreign body sensation, tearing, dry and itchy eyes. In advanced cases the pterygium can affect vision as it invades the cornea with the potential of obscuring the optical center of the cornea and inducing astigmatism and corneal scarring. Many patients do complain of the cosmetic appearance of the eye either with some of the symptoms above or as their major complaint.

A pterygium is a pinkish, triangular tissue growth on the cornea of the eye. It typically starts on the cornea near the nose. It may slowly grow but rarely grows so large that the pupil is covered. Often both eyes are involved.

The cause is unclear. It appears to be partly related to long term exposure to UV light and dust. Genetic factors also appear to be involved. It is a benign growth. Other conditions that can look similar include a pinguecula, tumor, or Terrien's marginal corneal degeneration.

Prevention may include wearing sunglasses and a hat if in an area with strong sunlight. Among those with the condition, an eye lubricant can help with symptoms. Surgical removal is typically only recommended if the ability to see is affected. Following surgery a pterygium may recur in around half of cases.

The frequency of the condition varies from 1% to 33% in various regions of the world. It occurs more commonly among males than females and in people who live closer to the equator. The condition becomes more common with age. The condition has been described since at least 1000 BC.

Pterygium inversum unguis (also known as "Pterygium inversus unguis," and "Ventral pterygium") is characterized by the adherence of the distal portion of the nailbed to the ventral surface of the nail plate. The condition may be present at birth or acquired, and may cause pain with manipulation of small objects, typing, and close manicuring of the nail.

Benign fibrous histiocytomas (also known as dermal dendrocytoma, dermatofibroma, fibrous dermatofibroma, fibrous histiocytoma, fibroma simplex, nodular subepidermal fibrosis, and sclerosing hemangioma) are benign skin growths.

Dermatofibromas are hard solitary slow-growing papules (rounded bumps) that may appear in a variety of colours, usually brownish to tan; they are often elevated or pedunculated. A dermatofibroma is associated with the dimple sign; by applying lateral pressure, there is a central depression of the dermatofibroma. Although typical dermatofibromas cause little or no discomfort, itching and tenderness can occur. Dermatofibromas can be found anywhere on the body, but most often they are found on the legs and arms. They occur most often in women; the male to female ratio is about 1:4. The age group in which they most commonly occur is 20 to 45 years.

Some physicians and researchers believe dermatofibromas form as a reaction to previous injuries such as insect bites or thorn pricks. They are composed of disordered collagen laid down by fibroblasts. Dermatofibromas are classed as benign skin lesions, meaning they are completely harmless, though they may be confused with a variety of subcutaneous tumours. Deep penetrating dermatofibromas may be difficult to distinguish, even histologically, from rare malignant fibrohistocytic tumours like dermatofibrosarcoma protuberans.

Dermatofibromas typically have a positive "buttonhole sign", or central dimpling in the center.

Many conditions affect the human integumentary system—the organ system covering the entire surface of the body and composed of skin, hair, nails, and related muscle and glands. The major function of this system is as a barrier against the external environment. The skin weighs an average of four kilograms, covers an area of two square meters, and is made of three distinct layers: the epidermis, dermis, and subcutaneous tissue. The two main types of human skin are: glabrous skin, the hairless skin on the palms and soles (also referred to as the "palmoplantar" surfaces), and hair-bearing skin. Within the latter type, the hairs occur in structures called pilosebaceous units, each with hair follicle, sebaceous gland, and associated arrector pili muscle. In the embryo, the epidermis, hair, and glands form from the ectoderm, which is chemically influenced by the underlying mesoderm that forms the dermis and subcutaneous tissues.

The epidermis is the most superficial layer of skin, a squamous epithelium with several strata: the stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum basale. Nourishment is provided to these layers by diffusion from the dermis, since the epidermis is without direct blood supply. The epidermis contains four cell types: keratinocytes, melanocytes, Langerhans cells, and Merkel cells. Of these, keratinocytes are the major component, constituting roughly 95 percent of the epidermis. This stratified squamous epithelium is maintained by cell division within the stratum basale, in which differentiating cells slowly displace outwards through the stratum spinosum to the stratum corneum, where cells are continually shed from the surface. In normal skin, the rate of production equals the rate of loss; about two weeks are needed for a cell to migrate from the basal cell layer to the top of the granular cell layer, and an additional two weeks to cross the stratum corneum.

The dermis is the layer of skin between the epidermis and subcutaneous tissue, and comprises two sections, the papillary dermis and the reticular dermis. The superficial papillary dermis with the overlying rete ridges of the epidermis, between which the two layers interact through the basement membrane zone. Structural components of the dermis are collagen, elastic fibers, and ground substance. Within these components are the pilosebaceous units, arrector pili muscles, and the eccrine and apocrine glands. The dermis contains two vascular networks that run parallel to the skin surface—one superficial and one deep plexus—which are connected by vertical communicating vessels. The function of blood vessels within the dermis is fourfold: to supply nutrition, to regulate temperature, to modulate inflammation, and to participate in wound healing.

The subcutaneous tissue is a layer of fat between the dermis and underlying fascia. This tissue may be further divided into two components, the actual fatty layer, or panniculus adiposus, and a deeper vestigial layer of muscle, the panniculus carnosus. The main cellular component of this tissue is the adipocyte, or fat cell. The structure of this tissue is composed of septal (i.e. linear strands) and lobular compartments, which differ in microscopic appearance. Functionally, the subcutaneous fat insulates the body, absorbs trauma, and serves as a reserve energy source.

Conditions of the human integumentary system constitute a broad spectrum of diseases, also known as dermatoses, as well as many nonpathologic states (like, in certain circumstances, melanonychia and racquet nails). While only a small number of skin diseases account for most visits to the physician, thousands of skin conditions have been described. Classification of these conditions often presents many nosological challenges, since underlying etiologies and pathogenetics are often not known. Therefore, most current textbooks present a classification based on location (for example, conditions of the mucous membrane), morphology (chronic blistering conditions), etiology (skin conditions resulting from physical factors), and so on. Clinically, the diagnosis of any particular skin condition is made by gathering pertinent information regarding the presenting skin lesion(s), including the location (such as arms, head, legs), symptoms (pruritus, pain), duration (acute or chronic), arrangement (solitary, generalized, annular, linear), morphology (macules, papules, vesicles), and color (red, blue, brown, black, white, yellow). Diagnosis of many conditions often also requires a skin biopsy which yields histologic information that can be correlated with the clinical presentation and any laboratory data.

A limbal nodule is any nodular lesion at the limbus (junction of the cornea and sclera) of the eye.

The differential diagnosis for a limbal nodule can include:

- Pinguecula

- Early Pterygium

- Foreign body / foreign body granuloma

- Phlycten, an inflamed nodule of lymphoid tissue

- Episcleritis

- Scleritis

- Granuloma

- Limbal dermoid, a kind of choristoma (NB: in other organs "dermoid" can refer to a teratoma)

- malignant melanoma

On babies, webbed neck may look like loose folds of skin on the neck. As the child grows, the skin may stretch out to look like there is little or no neck.

Multiple pterygium syndrome is a cutaneous condition inherited in an autosomal dominant fashion.

Neurocutaneous melanosis is associated with the presence of either giant congenital melanocytic nevi or non-giant nevi of the skin. It is estimated that neurocutaneous melanosis is present in 2% to 45% of patients with giant congenital melanocytic nevi. Patients with non-giant congenital melanocytic nevi seem to have a much lower, but undefined risk. Of these patients, only a small number are symptomatic, usually displaying symptoms before the age of 2.

These symptoms are the result of melanocytic lesions being present in the leptomeninges of the central nervous system.

Symptoms can include:

- Papilledema

- Cranial palsies

- Headache

- Vomiting

- Seizures

Others symptoms may also exist that are related to an increase in intracranial pressure. These symptoms seem to be present regardless of the malignancy of the melanin deposits within the central nervous system.

Approximately 10% of patient with neurocutaneous melanosis also present the Dandy–Walker syndrome and associated Dandy-Walker malformation. This malformation involves an enlargement of the posterior fossae and fourth ventricle along with agenesis of the cerebellar vermis. The abnormalities of the leptomeninges during fetal development due to neurocutaneous melanosis may be the cause of this increased incidence of the Dandy-Walker malformation. The development of hydrocephalus is the most common symptom associated with a combination of neurocutaneous melanosis and a Dandy-Walker malformation, occurring in about two out of three patients.

Overjet is the extent of horizontal (anterior-posterior) overlap of the maxillary central incisors over the mandibular central incisors. In class II (division I) malocclusion the overjet is increased as the maxillary central incisors are protruded.

It is a feature of Turner syndrome (only found in girls) and Noonan syndrome, as well as the rarer Klippel-Feil syndrome, or Diamond-Blackfan Anemia

Pterygium unguis (also known as "Dorsal pterygium") forms as a result of scarring between the proximal nailfold and matrix, with the classic example being lichen planus, though it has been reported to occur as a result of sarcoidosis and Hansen's disease.

CGCG lesions are found more commonly in the anterior of the maxilla and the mandible in younger people (before age 20). They are characterized by large lesions that expand the cortical plate and can resorb roots and move teeth. They are composed of multi-nucleated giant cells. CGCG has a slight predilection for females.

Radiographically :

It appears as multilocular radiolucencies of bone.The margin of the lesion has scalloped appearance and is well demarcated. Resorption and divergence of roots is also seen.

There are two types of CGCG's, non-aggressive and aggressive. The former has a slow rate of growth and thus less likely to resorb roots and perforate the cortical plate. The aggressive form has rapid growth and thus is much more likely to resorb roots and perforate the cortical plate. It also has a high rate for recurrence and can be painful and cause paresthesia.

Differential diagnosis to include: odontogenic keratocyst (OKC), ameloblastoma, odontogenic myxoma, hemangioma, central odontogenic fibroma, hyperparathyroid tumor, and cherubism.

Neurocutaneous melanosis is a congenital disorder characterized by the presence of congenital melanocytic nevi on the skin and melanocytic tumors in the leptomeninges of the central nervous system. These lesions may occur in the amygdala, cerebellum, cerebrum, pons, and spinal cord of patients. Although typically asymptomatic, malignancy occurs in the form of leptomeningeal melanoma in over half of patients. Regardless of the presence of malignancy, patients with symptomatic neurocutaneous melanosis generally have a poor prognosis with few treatment options. The pathogenesis of neurocutaneous melanosis is believed to be related to the abnormal postzygotic development of melanoblasts and mutations of the NRAS gene.

Central giant-cell granuloma (CGCG) is a benign condition of the jaws. It is twice as likely to affect women and is more likely to occur in 20- to 40-year-old people. Central giant-cell granulomas are more common in the mandible and often cross the midline.

CCCA usually begins at the central (sagittal) midline of the scalp. It is symmetric and exhibits scarring as the name suggests. It involves solely the top of the scalp or may progress to Hamilton–Norwood scale Type VI or VII. Early symptoms may include pruritus, dysesthesias and tenderness. On examination the skin is thin with few follicular ostia and later in the disease the scalp may appear shiny.

Clinical expressions of PPS are highly variable, but include the following:

- Limb findings: an extensive web running from behind the knee down to the heel (90%), malformed toenails, and webbed toes.

- Facial findings: cleft palate with or without cleft lip (75%), pits in the lower lip (40%), and fibrous bands in the mouth known as syngnathia (25%).

- Genital findings (50%): hypoplasia of the labia majora, malformation of the scrotum, and cryptorchidism.

Although lichen planus can present with a variety of lesions, the most common presentation is as a well defined area of purple-coloured, itchy, flat-topped papules with interspersed lacy white lines (Wickham's striae). This description is known as the characteristic "6 Ps" of lichen planus: planar (flat-topped), purple, polygonal, pruritic, papules, and plaques. This rash, after regressing, is likely to leave an area of hyperpigmentation that slowly fades. That said, a variety of other lesions can also occur.

A pinguecula is a common type of conjunctival degeneration in the eye.

Variants of cutaneous lichen planus are distinguished based upon the appearance of the lesions and/or their distribution. Lesions can affect the:

- Extremities (face, dorsal hands, arms, and nape of neck). This is more common in Middle Eastern countries in spring and summer, where sunlight appears to have a precipitating effect.

- Palms and soles

- Intertriginous areas of the skin. This is also known as "Inverse lichen planus."

- Nails characterized by irregular longitudinal grooving and ridging of the nail plate, thinning of the nail plate, pterygium formation, shedding of the nail plate with atrophy of the nail bed, subungual keratosis, longitudinal erthronychia (red streaks), and subungual hyperpigmentation. A sand-papered appearance is present in around 10% of individuals with nail lichen planus.

- Hair and Scalp. The scalp is rarely affected by a condition known as lichen planopilaris, acuminatus, follicular lichen planus, and peripilaris, characterised by violaceous, adherent follicular scale with progressive scarring alopecia. While lichen planus and lichen planopilaris may occur together, aside from sharing the term ‘lichen’ and revealing inflammation on skin biopsy, there is neither established data on their co-occurrence nor data to suggest a common etiology. Lichen planopilaris is considered an orphan disease with no definitive prevalence data and no proven effective treatments.

Other variants may include:

- "Lichen planus pemphigoides" characterized by the development of tense blisters atop lesions of lichen planus or the development vesicles de novo on uninvolved skin.

- "Keratosis lichenoides chronica" (also known as "Nekam's disease") is a rare dermatosis characterized by violaceous papular and nodular lesions, often arranged in a linear or reticulate pattern on the dorsal hands and feet, extremities, and buttock, and some cases manifest by sorrheic dermatitis-like eruption on the scalp and face; also palmo plantar keratosis has been reported.

- "Lichenoid keratoses" (also known as "Benign lichenoid keratosis," and "Solitary lichen planus") is a cutaneous condition characterized by brown to red scaling maculopapules, found on sun-exposed skin of extremities. Restated, this is a cutaneous condition usually characterized by a solitary dusky-red to violaceous papular skin lesion.

- "Lichenoid dermatitis" represents a wide range of cutaneous disorders characterized by lichen planus-like skin lesions.

Clinical diagnosis based on orofacial clefts and lip pits typically occurs shortly after birth. Certain defects may be difficult to diagnose, particularly a submucous cleft palate. This form of CP may not be detected except through finger palpation, as the mucosa covering the palate is intact, but the muscles underneath have lost their proper attachments. Feeding problems, impaired speech, and hearing loss are symptoms of a submucous cleft palate. Furthermore, approximately 15% of VWS cases with orofacial clefts, in the absence of prominent lip pits, cannot be easily distinguished from non-syndromic forms of orofacial clefting. Therefore, it is very important to closely examine these patients as well as their relatives for lip pits, especially when there is a family history of mixed clefting, in order to make the VWS diagnosis. Dentists may also play an important role in diagnosing cases not detected at birth, as they detect hypodontia commonly associated with VWS. The

patients most commonly lack the upper second premolars followed by the lower second premolars and upper lateral incisors. The absence of these teeth might play a role in the constricting of the dental arches.

The clinical signs seen in VWS are similar to those of popliteal pterygium syndrome (PPS), which is also an autosomal dominant disease. Approximately 46% of affected individuals have lip pits; other features include genital abnormalities, abnormal skin near nails, syndactyly of fingers and toes, and webbed skin. The disease is also caused by mutations in "IRF6"; however, they occur in the DNA-binding domain of "IRF6" and result in a dominant negative effect in which the mutated IRF6 transcription factor interferes with the ability of the wild type copy to function, in the case of a heterozygous individual.

Age: The mucocutaneous features of DKC typically develop between ages 5 and 15 years. The median age of onset of the peripheral cytopenia is 10 years.

Sex: The male-to-female ratio is approximately 3:1.

Physical: The triad of reticulated hyperpigmentation of the skin, nail dystrophy, and leukoplakia characterizes DKC. The syndrome is clinically heterogeneous; in addition to the diagnostic mucocutaneous features and bone marrow failure, affected individuals can have a variety of other clinical features.

Cutaneous findings:

The primary finding is abnormal skin pigmentation, with tan-to-gray hyperpigmented or hypopigmented macules and patches in a mottled or reticulated pattern. Reticulated pigmentation occurs in approximately 90% of patients. Poikilodermatous changes with atrophy and telangiectasia are common.

The cutaneous presentation may clinically and histologically resemble graft versus host disease. The typical distribution involves the sun-exposed areas, including the upper trunk, neck, and face. Other cutaneous findings may include alopecia of the scalp, eyebrows, and eyelashes; premature graying of the hair; hyperhidrosis; hyperkeratosis of the palms and soles; and adermatoglyphia (loss of dermal ridges on fingers and toes).

Nail findings:

Nail dystrophy is seen in approximately 90% of patients, with fingernail involvement often preceding toenail involvement.

Progressive nail dystrophy begins with ridging and longitudinal splitting. Progressive atrophy, thinning, pterygium, and distortion eventuate in small, rudimentary, or absent nails.

Mucosal findings:

Mucosal leukoplakia occurs in approximately 80% of patients and typically involves the buccal mucosa, tongue, and oropharynx. The leukoplakia may become verrucous, and ulceration may occur. Patients also may have an increased prevalence and severity of periodontal disease.

Other mucosal sites may be involved (e.g., esophagus, urethral meatus, glans penis, lacrimal duct, conjunctiva, vagina, anus). Constriction and stenosis can occur at these sites, with subsequent development of dysphagia, dysuria, phimosis, and epiphora.

Bone marrow failure:

Approximately 90% have peripheral cytopenia of one or more lineages. In some cases, this is the initial presentation, with a median age of onset of 10 years.

Bone marrow failure is a major cause of death, with approximately 70% of deaths related to bleeding and opportunistic infections as a result of bone marrow failure.

Pulmonary complications:

Approximately 20% of individuals with DKC develop pulmonary complications, including pulmonary fibrosis and abnormalities of pulmonary vasculature.

The recommendation is that DKC patients avoid taking drugs with pulmonary toxicity (e.g., busulfan) and that they have their lungs shielded from radiation during BMT.

Increased risk of malignancy:

Patients have an increased prevalence of malignant mucosal neoplasms, particularly squamous cell carcinoma of the mouth, nasopharynx, esophagus, rectum, vagina, or cervix. These often occur within sites of leukoplakia.

The prevalence of squamous cell carcinoma of the skin is also increased. Other malignancies reported include Hodgkin lymphoma, adenocarcinoma of the gastrointestinal tract, and bronchial and laryngeal carcinoma.

Malignancy tends to develop in the third decade of life.

Neurologic system findings: Patients may have learning difficulties and mental retardation.

Ophthalmic system findings: DKC reportedly is associated with conjunctivitis, blepharitides, and pterygium. Lacrimal duct stenosis resulting in epiphora (i.e., excessive tearing) occurs in approximately 80% of patients.

Skeletal system findings: Patients may have mandibular hypoplasia, osteoporosis, avascular necrosis, and scoliosis.

Gastrointestinal system findings: These may include esophageal webs, hepatosplenomegaly, enteropathy, and cirrhosis.

Genitourinary system findings:: Hypospastic testes, hypospadias, and ureteral stenosis are reported.

Female carriers: Female carriers of DKC may have subtle clinical features. One study showed that 3 of 20 female carriers had clinical features that included a single dystrophic nail, a patch of hypopigmentation, or mild leukoplakia.

Central centrifugal cicatricial alopecia (CCCA), also referred to as hot comb alopecia and follicular degeneration syndrome, is a type of alopecia first noticed in African Americans in the 1950s and reported by LoPresti et al. in 1968 as a result of application of petrolatum followed by a stove-heated iron comb. The original theory was that the hot petrolatum would travel down to the hair root, burn the follicle, and after repetitive injury scarring would result. Later CCCA was realized to affect men and women without a history significant for use of such styling techniques. Consequently, the terms "follicular degeneration syndrome" per Sperling and Sau in 1992 and then CCCA per Olsent et al. in 2003 were evolved. Plausible contributing factors may include other African-American styling techniques such as relaxers, tight braids, heavy extensions, certain oils, gels or pomades.

DKC can be characterized by cutaneous pigmentation, premature graying, of the nails, leukoplakia of the oral mucosa, continuous lacrimation due to atresia of the lacrimal ducts, often thrombocytopenia, anemia, testicular atrophy in the male carriers, and predisposition to cancer. Many of these symptoms are characteristic of geriatrics, and those carrying the more serious forms of the disease often have significantly shortened lifespans.