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Congenital Hypotrichosis
Congenital hypotrichosis is a broad term used to describe conditions in which hair is unusually sparse, reduced or absent from birth or early in life. It is not a single disease, but a diverse group of congenital and hereditary disorders affecting the development, structure or normal growth cycle of the hair follicle.
Some children are born with very little hair. Others may have relatively normal hair at birth and develop progressive thinning during childhood or adolescence. The scalp may be affected alone, or the eyebrows, eyelashes and body hair may also be involved.
Congenital hypotrichosis can occur as an isolated hair disorder or as part of a broader genetic syndrome. In syndromic forms, changes involving the teeth, nails, skin or other organ systems may provide important clues to the underlying diagnosis.
The causes of congenital hypotrichosis vary widely. Many forms are associated with inherited genetic changes affecting hair follicle development, hair shaft formation or the biological signals responsible for normal hair growth. Conditions that look similar can therefore have very different causes and patterns of inheritance.
Evaluation considers the age of onset, pattern of hair growth or loss, family history, appearance of the scalp and hair, and any other physical findings. Trichoscopy, microscopic examination of the hair shaft and, in some patients, genetic testing can help establish or clarify the diagnosis.
Accurate diagnosis is important because congenital hair disorders can sometimes be mistaken for acquired conditions such as alopecia areata. Treatment depends on the specific disorder. Some forms have no established therapy capable of restoring normal hair growth, while others may benefit from supportive treatment, cosmetic options or management of associated medical conditions. Genetic counseling may also be appropriate.
Aplasia Cutis Congenita
Aplasia cutis congenita is a rare developmental condition in which an infant is born with a localized area where the skin has not completely formed. It occurs most commonly on the scalp and may appear as an open lesion at birth or as an area that has already healed before delivery.
When the scalp is involved, hair follicles may be absent within the affected area, leaving a permanent patch of scarring hair loss after healing. The size and depth of the defect vary considerably. Small superficial lesions may heal with limited intervention, while larger defects can involve deeper tissues, including the skull, and may require specialized surgical management.
Aplasia cutis congenita is not a primary hair growth disorder in the same sense as hereditary hypotrichosis. Hair loss occurs because normal hair bearing skin and follicles are absent or have been replaced by scar tissue within the developmental defect.
Temporal Triangular Alopecia
Temporal triangular alopecia is a benign, localized form of nonscarring hair loss that most commonly affects the temple area of the scalp. The affected area is often triangular or spear shaped and usually remains stable rather than progressively expanding.
Temporal triangular alopecia was historically called congenital triangular alopecia, but that older name can be misleading because the condition is not always apparent at birth. Many cases become noticeable during early childhood as the surrounding scalp hairs become thicker and longer. Hair follicles remain present within the affected area, but they predominantly produce fine, short vellus hairs rather than the thicker terminal hairs normally found on the scalp.
Trichoscopy can help distinguish temporal triangular alopecia from alopecia areata and other causes of localized hair loss. The condition is harmless and generally does not require medical treatment. When the appearance is a significant concern, cosmetic approaches may be considered, and in carefully selected patients with a stable area, hair transplantation can sometimes provide improvement.
Congenital Atrichia With Papular Lesions
Congenital atrichia with papular lesions is a rare inherited form of permanent hair loss caused by changes in the HR gene, also known as the hairless gene. The condition is generally inherited when a child receives an altered copy of the gene from both parents.
Despite the word congenital in its name, affected infants may be born with apparently normal scalp hair. During the first months of life, the hair is progressively shed and does not return. Small keratin filled bumps, known as papules, may later develop on the scalp, face or other areas of the body.
Congenital atrichia with papular lesions is particularly important to recognize because it can be mistaken for alopecia universalis, a severe form of alopecia areata involving widespread loss of scalp and body hair. The distinction matters because congenital atrichia is a genetic disorder rather than an autoimmune disease, and treatments intended to suppress an immune attack on the hair follicle are not expected to restore normal hair growth.
Clinical examination, family history, skin findings and genetic testing can help establish the diagnosis and prevent unnecessary treatment. At present, there is no established medical therapy capable of restoring normal hair growth in congenital atrichia with papular lesions.
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