The presentation may be of alopecia (baldness). Individuals vary in severity of symptoms. Nail deformities may also be present as well as hair follicle keratosis and follicular hyperkeratosis.

Hair diseases are disorders primarily associated with the follicles of the hair.

A few examples are

- Alopecia

- Bubble hair deformity

- Hair casts

- Hair loss

- hypertrichosis

- Ingrown hair

- Monilethrix

- Premature greying of hair

- Pattern hair loss

- Trichorrhexis invaginata

Many hair diseases can be associated with distinct underlying disorders.

Piedra are fungal diseases.

Hair disease may refer to excessive shedding or baldness (or both). Balding can be localised or diffuse, scarring or non-scarring. Increased hair can be due to hormonal factors (hirsutism) or non-hormonal (hypertrichosis). Scalp disorders may or may not be associated with hair loss.

Monilethrix (also referred to as beaded hair) is a rare autosomal dominant hair disease that results in short, fragile, broken hair that appears beaded. It comes from the Latin word for necklace ("monile") and the Greek word for hair ("thrix").

Hidrotic ectodermal dysplasia 2, or Clouston syndrome (referred to as HED2 throughout this entry) is characterized by partial or total alopecia, dystrophy of the nails, hyperpigmentation of the skin (especially over the joints), and clubbing of the fingers. Sparse scalp hair and dysplastic nails are seen early in life. In infancy, scalp hair is wiry, brittle, patchy, and pale; progressive hair loss may lead to total alopecia by puberty. The nails may be milky white in early childhood; they gradually become dystrophic, thick, and distally separated from the nail bed. Palmoplantar keratoderma may develop during childhood and increases in severity with age. The clinical manifestations are highly variable even within the same family.

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.

Symptoms include lack of sweat glands, thin hair, brittle nails, mottled skin, and lack of fingerprints.

One of the principle symptoms of GAPO syndrome is growth retardation, caused by slow skeletal formation and results in individuals being below average height. Alopecia, or hair loss, is another key indication of GAPO syndrome. Their hair is typically thinly dispersed, and fragile, which often leads to baldness later in life. Similarly, tooth growth is stunted, with teeth failing to emerge form the gums or otherwise develop normally. Atrophy of the optic nerve occurs in approximately one third of individuals. This degradation leads to inhibited peripheral vision, and increased difficulty distinguishing colours.

While not a defining feature, most sufferers of GAPO syndrome have coarse facial features, and abnormal structure of the middle portion of their faces, typically coupled with a large forehead. Individuals with the disease tend to have depressed nose bridges, protruding ears, and abnormally thick lips, though these symptoms are not unique to this disorder.

No direct correlation has been found between GAPO syndrome and mental retardation, though cases of individuals having both have been reported.

Due to the severity of the phenotype, GAPO syndrome can be diagnosed very early on. Most cases can be diagnosed by 6 months of age, and most symptoms will be apparent by age 2.

Alopecia totalis is the loss of all skull and facial hair. Its causes are unclear, but believed to be autoimmune.

Kinking hair (also known as "Acquired progressive kinking") is a condition primarily reposted in postpubescent males with androgenetic alopecia, presenting with gradual curling and darkening of the frontal, temporal, auricular, and vertex hairs which, under the microscope, show kinks and twists with or without longitudinal grooving.

Dermatopathia pigmentosa reticularis (DPR), also known as dermatopathia pigmentosa reticularis hyperkeratotica et mutilans, dermatopathia pigmentosa reticularis hypohidotica et atrophica and dermatopathic pigmentosa reticularis, is a rare, autosomal dominant congenital disorder that is a form of ectodermal dysplasia. Dermatopathia pigmentosa reticularis is composed of the triad of generalized reticulate hyperpigmentation, noncicatricial alopecia, and onychodystrophy.

Trachyonychia, sometimes called sandpapered nails, is a condition characterized by rough accentuated linear ridges (longitudinal striations) on the nails of the fingers and toes. When the condition occurs on all the twenty nails of the fingers and toes, it is known as twenty-nail dystrophy, most evident in childhood, favoring males.

Trachyonychia causes the nails to become opalescent, thin, dull, fragile, and finely longitudinally ridged, and, as a result, distally notched. It can be a manifestation of lichen planus, psoriasis, alopecia areata, immunoglobulin A deficiency, atopic dermatitis, and ichthyosis vulgaris.

"The longitudinal striations can occur as a normal part of the aging process", and not until the nails start to thin and get a sandpaper look is the condition called trachonychia. The nails are opalescent and frequently are brittle and split at the free margin. There has been evidence of the condition as a cutaneous manifestation of lichen planus. It has also been associated with other diseases such as eczema, psoriasis, alopecia areata, and atopic dermatitis. Trachonychia is often seen in vitiligo patients – suggesting that they are more susceptible to this condition.

Histopathologic features include a perifollicular lymphocytic infiltrate, concentric lamellar fibrosis (layers of fibroblasts in the papillary dermis), sebaceous gland loss and premature disintegration of the internal root sheath. Additionally, granulomatous inflammation secondary to follicular rupture has been noted. Perifollicular erythema and follicular keratosis is usually absent.

Clouston's hidrotic ectodermal dysplasia (also known as "Alopecia congenita with keratosis palmoplantaris," "Clouston syndrome," "Fischer–Jacobsen–Clouston syndrome," "Hidrotic ectodermal dysplasia," "Keratosis palmaris with drumstick fingers," and "Palmoplantar keratoderma and clubbing") is caused by mutations in a connexin gene, GJB6 or connexin-30, characterized by scalp hair that is wiry, brittle, and pale, often associated with patchy alopecia.

Important diagnoses to consider include female pattern hair loss (FPHL), chronic telogen effluvium (CTE), and alopecia areata (AA). FPHL is a non-scarring progressive miniaturization of the hair follicle with one of three different characteristic patterns. CTE is an idiopathic disease causing increased hair shedding and bi-temporal recession, usually in middle aged women. AA is an autoimmune attack of hair follicles that usually causes hair to fall out in small round patches.

There is loss of both terminal and vellus hairs that occurs in a bandlike pattern on the frontotemporal scalp. It is a scarring alopecia that has been associated with a loss of eyebrows, facial papules, glabellar red dots, and prominent venous vasculature in the forehead. Facial hyperpigmentation may occur in dark-skinned patients, if association with lichen planus pigmentosus is present.

Nevus psiloliparus is a cutaneous condition, a rare scalp anomaly characterized by a variable degree of alopecia and an excessive amount of adipose tissue.

It is the main hallmark of encephalocraniocutaneous lipomatosis (ECCL), otherwise known as Haberland syndrome.

GAPO syndrome is a rare, autosomal recessive disorder that causes severe growth retardation, and has been observed fewer than 30 times before 2011. GAPO is an acronym that encompasses the predominant traits of the disorder: growth retardation, alopecia, pseudoanodontia (teeth failing to emerge from the gums), and worsening optic atrophy in some subjects. Other common symptoms include premature aging, large, prominent foreheads, and delayed bone aging. GAPO syndrome typically results in premature death around age 30-40, due to interstitial fibrosis and atherosclerosis.

ANOTHER syndrome consists of alopecia, nail dystrophy, ophthalmic complications, thyroid dysfunction, hypohidrosis, ephelides and enteropathy, and respiratory tract infections. This is an autosomal recessive variant of ectodermal dysplasia.

Symptoms of hair loss include hair loss in patches usually in circular patterns, dandruff, skin lesions, and scarring. Alopecia areata (mild – medium level) usually shows in unusual hair loss areas e.g. eyebrows, backside of the head or above the ears where usually the male pattern baldness does not affect. In male-pattern hair loss, loss and thinning begin at the temples and the crown and either thins out or falls out. Female-pattern hair loss occurs at the frontal and parietal.

People have between 100,000 and 150,000 hairs on their head. The number of strands normally lost in a day varies, but on average is 100. In order to maintain a normal volume, hair must be replaced at the same rate at which it is lost. The first signs of hair thinning that people will often notice are more hairs than usual left in the hairbrush after brushing or in the basin after shampooing. Styling can also reveal areas of thinning, such as a wider parting or a thinning crown.

Individuals with acrodermatitis enteropathica may present with the following:

- Blistering of skin

- Dry skin

- Emotional lability

- Glossitis

- Pustule

Alopecia (loss of hair from the scalp, eyebrows, and eyelashes) may occur. Skin lesions may be secondarily infected by bacteria such as "Staphylococcus aureus" or fungi such as "Candida albicans". These skin lesions are accompanied by diarrhea.

Robinow noted the resemblance of affected patients' faces to that of a fetus, using the term "fetal facies" to describe the appearance of a small face and widely spaced eyes. Clinical features also may include a short, upturned nose, a prominent forehead, and a flat nasal bridge. The upper lip may be "tented", exposing dental crowding, "tongue tie", or gum hypertrophy.

Though the eyes do not protrude, abnormalities in the lower eyelid may give that impression. Surgery may be necessary if the eyes cannot close fully. In addition, the ears may be set low on the head or have a deformed pinna.

Patients suffer from dwarfism, short lower arms, small feet, and small hands. Fingers and toes may also be abnormally short and laterally or medially bent. The thumb may be displaced and some patients, notably in Turkey, experience ectrodactyly. All patients often suffer from vertebral segmentation abnormalities. Those with the dominant variant have, at most, a single butterfly vertebra. Those with the recessive form, however, may suffer from hemivertebrae, vertebral fusion, and rib anomalies. Some cases resemble Jarcho-Levin syndrome or spondylocostal dysostosis.

Genital defects characteristically seen in males include a micropenis with a normally developed scrotum and testes. Sometimes, testicles may be undescended, or the patient may suffer from hypospadias. Female genital defects may include a reduced size clitoris and underdeveloped labia minora. Infrequently, the labia majora may also be underdeveloped. Some research has shown that females may experience vaginal atresia or haematocolpos.

The autosomal recessive form of the disorder tends to be much more severe. Examples of differences are summarized in the following table:

The syndrome is characterized by alopecia, hypogonadism, hypothyroidism, hearing loss, intellectual disability and diabetes mellitus. Electrocardiogram anomalies have also been reported.

Hypotrichosis–lymphedema–telangiectasia syndrome is a congenital syndrome characterized by lymphedema (swelling of tissue due to malformation or malfunction of lymphatics), the presence of telegiectasias (small dilated vessels near the surface of the skin), and hypotrichosis or alopecia (hair loss). Lymphedema usually develops in the lower extremities during puberty. Hair is normal at birth, but usually lost during infancy. Telangiectasias may present on the palms and soles more commonly than on the scalp, legs, and genitalia. The syndrome has been reported in association with both autosomal dominant and autosomal recessive inheritance patterns.

It is associated with a rare mutation of the transcription factor gene "SOX18".

Alopecia universalis can occur at any age, and is currently believed to be an autoimmune disorder, in which a person's immune system attacks the hair follicles. Genetic factors may contribute to AU as approximately 20% of those affected have a family member with alopecia.

Ophiasis is a form of alopecia areata characterized by the loss of hair in the shape of a wave at the circumference of the head.

It gets its name from "ophis", which is the Greek word for snake, because of the apparent similarity to a snake-shape and the pattern of hair loss.

The term "sisaipho" is used to characterize the inverse pattern. Sisaipho is the reverse spelling of ophiasis. It is also called "ophiasis inversus".