Background
Loose anagen syndrome was first described in 1984. It is a hair disorder characterized by anagen hairs of abnormal morphology that are easily and painlessly pulled or plucked from the scalp. Hair is thinned in appearance and typically does not grow beyond the nape of the neck.
Pathophysiology
The precise pathogenesis of loose anagen syndrome is not known, but theories postulating an abnormality in the hair's anchoring mechanism predominate. [1] SHOC2 mutations may be linked with ectodermal abnormalities, including loose anagen hair. [2]
The inner root sheath is thought to play an integral role in anchoring the hair shaft within the follicle. In loose anagen syndrome, mutations in genes coding for cytokeratins have been identified in some cases and are thought to result in abnormal keratinization of the inner root sheath. [3] This faulty keratinization leads to impaired adherence of the deformed hair shafts to their follicles. The impaired attachment may result in premature cessation of the anagen phase and account for reduced hair length. One author has also reported reduced follicle size due to delayed maturation. This may be responsible for sparse hair growth.
Etiology
Although its occurrence is typically sporadic, familial cases of loose anagen syndrome have been observed. Inheritance appears to be in an autosomal dominant pattern with variable penetrance. Loose anagen syndrome has not been consistently associated with any other disorder; however, individual cases associated with the following syndromes have been reported (associations were most likely coincidental):
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Ocular coloboma syndrome [6]
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Trichorhinophalangeal syndrome
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Nail-patella syndrome
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Hypohidrotic ectodermal dysplasia and ectrodactyly-ectodermal dysplasia-clefting syndrome [7]
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Acquired immunodeficiency syndrome
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Woolly hair [8]
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Alopecia areata
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Colobomas and dysmorphic features including low-set ears, hypertelorism, left microphthalmia, frontal bossing, a thin upper lip, a simple philtrum, and slight left facial hypoplasia [12]
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Noonan-like syndrome characterized by short stature, a distinctive facial phenotype, macrocephaly, enlarged cerebral spinal fluid spaces, a short neck with redundant skin, severe growth hormone deficiency, mild psychomotor delay with attention deficit/hyperactivity disorder, and increased skin pigmentation [13, 14]
Epidemiology
Frequency
United States
The prevalence of loose anagen syndrome is unknown. Although recently described, loose anagen syndrome may actually be rather common. It is undoubtedly often misdiagnosed as alopecia areata or trichotillomania. [15] It has likely been both underdiagnosed and underreported to date.
International
The incidence and prevalence of loose anagen syndrome are unknown. It may be underreported, particularly in boys. [16]
Race
Loose anagen syndrome has been reported overwhelmingly in white persons. Most but not all are light complexioned with fine blond hair. However, it may be rarely evident in individuals of African or Asian descent. [17, 18]
Sex
The syndrome is more common in females than in males.
Age
The classic patient with loose anagen syndrome is a girl aged 2-5 years with blonde hair; however, cases of loose anagen syndrome in boys, in adults, and in individuals with dark hair have also been reported.
Prognosis
The diffuse hair loss that occurs in loose anagen syndrome often raises considerable concern among patients, parents, and clinicians. In individuals who are affected, hair typically increases in length and density over time and darkens in color; however, the loose anagen characteristic persists and hair continues to be easily and painlessly pulled from the scalp. Although no treatment is currently available, the condition is of cosmetic significance only, and symptoms generally improve over time.
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Thinning, dull, lackluster blonde hair with matting over the occipital region.
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Microscopic view of easily plucked hair demonstrating a distorted anagen bulb lacking inner and outer root sheaths, and a ruffled, sawtooth, baggy-stocking appearance of the cuticle (original magnification X100).
