Loose Anagen Hair Syndrome.

Sir,

Loose anagen hair syndrome (LAHS) is a rare, benign, self-limiting condition where anagen hairs are easily and painlessly extracted. It was originally described in children who had sparse hair that did not grow long.[1] It was first reported in the literature, in 1986, by Nodl and later by Zaun as syndrome of loosely attached hair in childhood.[2] LAHS occurs sporadically, or it is inherited as an autosomal dominant trait with variable expressivity. It is seen mainly in female children between 2 and 6 years of age as it is underdiagnosed in boys due to hairstyle difference. Knowledge about this entity and the strong suspicion is necessary in children as it may go underdiagnosed and may lead to an array of investigations and treatment modalities. We here in describe a case of LAHS in a young child.

A 3-year-old female child presented with sparse hair on the scalp from 2 years. Mother gives a history that her child's hair is sparse on the scalp and not growing. Her developmental milestones were normal. There was no history of plucking of the hairs. Past history was noncontributory. General physical examination was normal. Cutaneous examination revealed sparse, thin, fine hairs all over the scalp more on the temporoparietal region [Figure 1]. The hair pull test was positive. Other areas of the body were normal. Systemic examination was normal. Investigations showed normal blood counts and serum chemistry profile. Hair trichogram showed >70% anagen hairs with ruffled cuticle resembling floppy sock appearance [Figure 2a]. Some of the hairs examined showed hair bulb bent at an acute angle to the shaft resembling mouse-tail appearance [Figure 2b]. Based on the above findings diagnosis of LAHS was considered. Parents were reassured about the condition, and the child is on regular follow-up.

Figure 1

Thin, fine, sparse hairs present on temporoparietal region

Figure 2

(a) Trichogram showing distorted and ruffled cuticle resembling floppy sock appearance (b) hair bulb bent at acute angle to hair shaft resembling mouse tail

The exact pathogenesis of LAHS is not known. One theory is that there is a premature keratinization of inner root sheath that produces an impaired adhesion between the cuticle of the inner root sheath and cuticle of the hair shaft. There are reports that mutation in the gene encoding for companion layer keratin (K6HF) in a family with LAHS.[3] Not all hair follicles are involved in LAHS. Clinically presents as sparse, fine, thin hairs or either patchy or diffuse alopecia on the scalp. Rarely, eyebrows and body hair have been reported. There is a typical history that child's hair is not growing and seldom requires a haircut. There are 3 clinical phenotypes of LAHS: Type A characterized by decreases hair density, type B consists mainly unruly hair, type C is characterized by normal appearing hair with excessive shedding of loose anagen hairs.[4]

Diagnosis is essentially clinical, and the hallmark feature is ability to extract anagen hairs painlessly by hair pull test. At least 3–10 loose anagen hairs must be present for LAHS. Trichogram shows >70% of anagen hairs. Microscopy of hairs shows distorted and ruffling of the cuticle that has been describes as “floppy sock appearance” which is a characteristic sign of LAHS. Some of the hairs bulbs are angled to the shaft resembling mouse tail.[5] Histopathological examination shows premature keratinization of inner root sheath layer.

The differential diagnosis includes alopecia areata, trichotillomania, and telogen effluvium.[5] As LAHS has a benign nature prognosis is good. Reassurance and proper counseling are necessary. Topical minoxidil 5% lotion has been tried with good results. LAHS should always be considered as one of the differential diagnosis of diffuse noncicatricial alopecia in young children.

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Conflicts of interest

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