alopecia

Deficiency of the hair or wool coat; may be caused by failure to grow or by loss after growth. There is a significant difference amongst those in which grown fibers are lost, between those in which stumps of fibers remain, and those in which the hair root has been shed from the follicle. See also hypotrichosis, alopecic.

• a. areata — noninflammatory hair loss in sharply defined areas. A rare condition seen in dogs, cats, horses and primates; the cause is unknown, but immune-mediated mechanisms are suspected.
• bilaterally symmetric a. — a clinical feature associated with endocrine and metabolic causes of hair loss in dogs and cats, although other causes including self-trauma are sometimes responsible.
• cicatricial a., a. cicatrisata — irreversible loss of hair associated with scarring.
• collar frictional a. — loss of hair around the neck occurs in some cats wearing collars. It is reversible when the collar is removed.
• color dilution a. — color mutant alopecia (below).
• color mutant a. — a clinical syndrome seen in dogs with blue or fawn coat color caused by the dilution gene at the D locus. Clinical signs include bacterial folliculitis, scaling and hair loss, mainly over the back and commencing within the first year or two of life. Hairs contain clumped melanin (macromelanosomes) with distortion and fracture of the shaft. Seen most often in Doberman pinschers but reported in a number of other breeds. Called also blue Doberman syndrome, fawn Irish setter syndrome. Seen also in many breeds of cattle, especially Simmental, Angus. Characterized by short, sparse, curly haircoats and wispy tail switch. Called also color dilution alopecia.
• a. congenitalis — complete or partial absence of the hair at birth.
• endocrine a. — hair loss caused by an endocrine abnormality that adversely affects hair growth. Usually characterized by symmetrical distribution and noninflammatory changes in the skin.
• feline acquired symmetric a. — a bilaterally symmetric hair loss on the posterior abdomen, inner thighs, perineum and, less consistently, ventral thorax, flanks and forelegs of cats, most commonly neutered males. The skin is usually normal and nonpruritic. The cause is unknown; sex hormone deficiency was previously believed to be responsible, but abnormal thyroid function is also suspected. Some cases are in reality self-inflicted by excessive grooming or the cat's response to unrecognized pruritus. Called also feline endocrine alopecia.
• inherited symmetrical a. — calves born with a normal haircoat lose their hair over bilaterally distributed specific areas of the skin. See also inherited congenital hypotrichosis.
• a. medicamentosa — hair loss due to ingestion of a drug.
• a. mucinosa — hair loss associated with mucinosis of the epidermis and hair follicles.
• pattern a. — see pattern baldness.
• periodic a. — a pinnal alopecia observed in miniature poodles. Regrowth usually occurs in 3 to 4 months.
• pinnal a. — gradual loss of hair on the pinnae until there is total alopecia. Occurs mainly in Dachshunds and may have a hereditary basis.
• pituitary a. — see growth hormone-responsive dermatitis.
• post-clipping a. — a failure of hair to regrow, usually for a long period, after clipping. Seen particularly in Chow Chows, Samoyeds and Siberian huskies. The cause is unknown.
• postvaccination a. and panniculitis — a focal area of hair loss occurring at the site of rabies vaccination; miniature poodles are predisposed.
• progressive a., congenital anemia and dyskeratosis — a condition seen in Hereford cattle; affected calves are born with sparse, short kinky or curly hair which is gradually lost. They are also anemic.
• psychogenic a. — hair loss resulting from intensive self-trauma such as licking or biting and for which no cause can be found. Boredom is often considered a factor. See also acral lick dermatitis, idiopathic hyperesthesia syndrome.
• seasonal flank a. — a cyclic follicular dysplasia which tends to occur seasonally, mainly in spring or fall. There is a nonpruritic hair loss and often hyperpigmentation of the skin in irregular, defined areas on the flanks and lateral thorax. Many cases regrow hair after 3 to 6 months, but recurrences at the corresponding time in following years is common. Boxers, Airedale terriers, English bulldogs, and Miniature schnauzers are predisposed breeds, but it has been reported in others. Called also cyclic follicular dysplasia.
• symptomatic a., a. symptomatica — loss of hair due to systemic or psychogenic causes, such as general ill health, infections of the skin, nervousness, a specific disease, or to stress. The hair may fall out in patches, or there may be diffuse loss of hair instead of complete baldness in one area.
• traction a. — loss of hair due to traction, as occurs in dogs of breeds in which hair on the head is held by rubber bands or barrettes.
• traumatic a. — that caused by self-trauma (licking, scratching, chewing or pulling); possible in any pruritic skin disease in any species, but particularly severe in cats. The area of hair loss corresponds to those areas most accessible to the form of self-trauma.
• a. universalis — congenital absence of hair from the entire body. A characteristic of the Canadian hairless cat and Sphinx cat.