Tubular Hair Casts: A Close Look

A Handful of Inflammatory Hair Loss Disorders Frequently have Tubular Hair Casts

Scaling around hairs occurs in a number of disorders. When the scaling hugs or surrounds the hair shaft, it is often referred to as perifollicular scaling. When scaling not only surrounds the hairs but also climbs up the hair shaft such that the length of the scaling is greater than the width, the term ‘tubular scaling’ is used. Tubular scaling is is a type of proximal hair cast. Hair casts are cylindrical structures seen surroungin hairs. A variety of inflammatory disorders can give tubular casts.

Hair casts are thin, elongated, cylindrical concretions that encircle the hair shaft. Hair casts range in size from 2-7 mm and can be easily moved and dislodged. The term was coined back in 1957 by Kligman. Hair casts are said to be "primary" in nature when not associated with an underlying scalp disorder and "secondary" when associated with an underlying disorder. Common secondary causes include psoriasis, seborrheic dermatitis, pemphigus and traction alopecia and scarring alopecia. Many other causes are possible too including hair sprays and deodorants.
Hair casts are thought to represent material from both the internal root sheath and the external root sheath of the hair follicle.

Mathur et al 2019

In 2019, Mathur and colleagues set out to better understand some of the causes of tubular hair casts. They evaluated 214 cases of hair disorder after excluding conditions like seborrheic dermatitis, psoriasis, traction and trichotillomania. There were 57 cases of alopecia areata, 48 cases of androgenetic alopecia, 26 with pediculosis, 23 with tinea capitis, 19 with discoid lupus, 16 with lichen planopilaris, 10 with frontal fibrosing alopecia, 6 with pemphigus follicaceus, 3 with pemphigus vulgaris, 3 with folliculitis decalvans and 1 with wooly hair.

How common are tubular hairs casts?

Tubular hairs casts were seen in 21 of the 214 cases - so about 10 %. This inlcuded 50 % of pemphigus vulgaris, 30 % of frontal fibrosing alopecia, 26 % of discoid lupus, 25 % of lichen planopilaris, 20 % of pemphigus folliaceus and 17% of tinea capitis.

Scaling in Lichen planopilaris

There were 16 patients with LPP in the study. Tubular hair casts were found in 4 patients or 25%. Scaling was proximal in 75 % of those patients noted to have casts and both proximal and distal in 1 patient. In all 4 patients, there was just one cast noted on a hair and only one hair was ever enveloped by a cast. The surrounding scaling of the scalp skin was minimal to absent in all 4.

Scaling in Frontal Fibrosing Alopecia

There were 10 patients with FFA in the study. Tubular hair casts were found in 3 patients. Scaling was proximal in one of those patients, distal in one patient and both proximal and distal in one other. In all 3 patients, there was just one cast noted on a hair and only one hair was ever enveloped by a cast. The surrounding scaling of the scalp skin was minimal to absent in all 3.

Scaling in Discoid lupus

There were 19 patients with DLE in the study. Tubular hair casts were found in 5 patients. Scaling was proximal in one of those patients, distal in one patient and both proximal and distal in 3 others. In 3 patients, there was just one cast noted on a hair and in 2 there were 2 casts in a single hairs. Only one hair was ever enveloped by a cast. The surrounding scaling of the scalp skin was minimal to absent in 1, medium in 1 patient and extensive in 3 patients.

Patterns of Hair Casts

There were several patterns of casts. Most were proximal (ie 90 % of casts), meaning they where close to the skin where the hair emerged from the scalp. Some however were distal. Often there was just one cast per hairs, but was 2 observed in some cases. The cast usually wrapped around a single hair but in some cases the same cast enveloped 2 hairs.

In 2 cases of DLE and 1 case of alopecia areata, there were 2 casts noted on a single hairs. In one case of PF, the cast wrapped around 2 adjacent hairs. In PF, PV, and DLE the scaling of the scalp below was more likely to be extensive

REFERENCE

Mathur  M et al. Tubular Hair Casts in Trichoscopy of Hair and Scalp Disorders. Int J Trichology 2019 Jan-Feb;11(1):14-19.