page_title: List of skin conditions
section_title: Conditions of the skin appendages
hierarchical_section_title: List of skin conditions / Conditions of the skin appendages
caption_attribution_description: العربية: رأس مريض بالثعلبة. Deutsch: Alopecia Areata. English: Alopecia areata. Español: Alopecia areata. Italiano: Un esempio di alopecia areata classica. Polski: Łysienie plackowate. Türkçe: Saçkıran.
context_page_description: 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 metres, 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, 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.
context_section_description: Conditions of the skin appendages are those affecting the glands of the skin, hair, nails, and arrector pili muscles.
  Acne necrotica
  Acquired generalized hypertrichosis (acquired hypertrichosis lanuginosa, hypertrichosis lanuginosa acquisita)
  Acquired perforating dermatosis (acquired perforating collagenosis)
  Acrokeratosis paraneoplastica of Bazex (acrokeratosis neoplastica, Bazex syndrome)
  Acroosteolysis
  Acute paronychia 
  Alopecia areata
  Alopecia neoplastica
  Anagen effluvium
  Androgenic alopecia (androgenetic alopecia)
  Anhidrosis (hypohidrosis)
  Anonychia
  Apparent leukonychia
  Beau's lines
  Blue nails
  Bromidrosis (apocrine bromhidrosis, fetid sweat, malodorous sweating, osmidrosis)
  Bubble hair deformity
  Central centrifugal cicatricial alopecia (follicular degeneration syndrome, pseudopelade of the central scalp)
  Chevron nail (herringbone nail)
  Chromhidrosis (colored sweat)
  Chronic paronychia
  Cicatricial alopecia
  Clubbing (drumstick fingers, Hippocratic fingers, watch-glass nails)
  Congenital onychodysplasia of the index fingers
  Disseminate and recurrent infundibulofolliculitis
  Erosive pustular dermatitis of the scalp (erosive pustular dermatosis of the scalp)
  Erythromelanosis follicularis faciei et colli
  Folliculitis decalvans
  Folliculitis nares perforans
  Fox–Fordyce disease
  Frontal fibrosing alopecia
  Generalized congenital hypertrichosis (congenital hypertrichosis lanuginosa)
  Generalized hyperhidrosis
  Graham-Little syndrome
  Granulosis rubra nasi 
  Green nails
  Gustatory hyperhidrosis
  Hair casts (pseudonits)
  Hair follicle nevus (vellus hamartoma)
  Hairy palms and soles
  Half and half nails (Lindsay's nails)
  Hangnail
  Hapalonychia
  Hematidrosis
  Hirsutism
  Hook nail
  Hot comb alopecia
  Hypertrichosis cubiti (hairy elbow syndrome)
  Hypertrichosis simplex of the scalp
  Intermittent hair–follicle dystrophy
  Keratosis pilaris atrophicans
  Kinking hair (acquired progressive kinking)
  Koenen's tumor (Koenen's periungual fibroma, periungual fibroma)
  Koilonychia (spoon nails)
  Kyrle disease
  Leukonychia (white nails)
  Lichen planopilaris (acuminatus, follicular lichen planus, lichen planus follicularis, peripilaris)
  Lichen planus of the nails
  Lichen spinulosus (keratosis spinulosa)
  Lipedematous alopecia (lipedematous scalp)
  Localized acquired hypertrichosis
  Localized congenital hypertrichosis
  Longitudinal erythronychia
  Longitudinal melanonychia
  Loose anagen syndrome (loose anagen hair syndrome)
  Lupus erythematosus
  Madarosis
  Malalignment of the nail plate
  Male-pattern baldness
  Marie–Unna hereditary hypotrichosis (Marie–Unna hypotrichosis)
  Median nail dystrophy (dystrophia unguis mediana canaliformis, median canaliform dystrophy of Heller, solenonychia)
  Mees' lines
  Melanonychia
  Menkes kinky hair syndrome (kinky hair disease, Menkes disease)
  Monilethrix (beaded hair)
  Muehrcke's nails (Muehrcke's lines) 
  Nail–patella syndrome (Fong syndrome, hereditary osteoonychodysplasia, HOOD syndrome)
  Neoplasms of the nailbed
  Nevoid hypertrichosis
  Noncicatricial alopecia
  Onychauxis
  Onychoatrophy
  Onychocryptosis (ingrown nail, unguis incarnatus)
  Onychogryphosis (ram's horn nails)
  Onycholysis
  Onychomadesis
  Onychomatricoma
  Onychophagia (nail biting)
  Onychophosis
  Onychoptosis defluvium (alopecia unguium)
  Onychorrhexis (brittle nails)
  Onychoschizia
  Onychotillomania
  Ophiasis
  Palmoplantar hyperhidrosis (emotional hyperhidrosis)
  Parakeratosis pustulosa
  Patterned acquired hypertrichosis
  Perforating folliculitis
  Pili annulati (ringed hair)
  Pili bifurcati
  Pili multigemini
  Pili pseudoannulati (pseudo pili annulati)
  Pili torti (twisted hairs)
  Pincer nails (omega nails, trumpet nails)
  Pityriasis amiantacea (tinea amiantacea)
  Platonychia
  Plica neuropathica (felted hair)
  Plummer's nail
  Premature greying of hair
  Prepubertal hypertrichosis
  Pressure alopecia (postoperative alopecia, pressure-induced alopecia)
  Pseudofolliculitis barbae (barber's itch, folliculitis barbae traumatica, razor bumps, scarring pseudofolliculitis of the beard, shave bumps)
  Pseudopelade of Brocq (alopecia cicatrisata)
  Psoriatic nails
  Pterygium inversum unguis (pterygium inversus unguis, ventral pterygium)
  Pteryg
caption: Alopecia areata
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