Acquired Diffuse Trichomalacia Associated With Prolonged Use of a Detangling Hairbrush

Abstract

This case series reports on cases of diffuse alopecia with trichomalacia after use of a detangling hairbrush.

Detangling hairbrushes have flexible bristles of varying lengths and rounded tips to control unruly hair without excessive force on hair shafts. We report 3 cases of diffuse alopecia with trichomalacia after the use of a detangling hairbrush and the presence of corkscrew hairs on trichoscopy.

Methods

This case series involved a chart review of 3 patients with alopecia associated with the use of a detangling hairbrush (eFigure in Supplement 1) seen at our center between 2020 and 2022. The National Healthcare Group Domain Specific Review Board approved the study (approval reference 2022/00672), and patients provided written informed consent.

Results

Case 1

A woman in her 20s presented with diffuse alopecia after using a detangling hairbrush for 6 months. Trichoscopy showed coiled and corkscrew hairs amid broken hairs (Figure 1A). Scalp biopsy showed noncicatricial alopecia, with 35% of hair follicles with trichomalacia and a mildly decreased anagen:telogen ratio (76%:24%) (Figure 2A). She stopped using the hairbrush, but distorted hair follicles and corkscrew hairs were still appreciated 12 months later.

Figure 1. Trichoscopy.

Trichoscopy showing broken hairs (yellow arrowheads), kinked hair shafts (blue asterisks), and corkscrew hairs (red dashed circles). These findings were present diffusely throughout the scalp.

Figure 2. Scalp Biopsy.

Transverse section of a scalp punch biopsy showing several hair follicles with trichomalacia (yellow arrowheads) (hematoxylin-eosin; original magnification ×80).

Case 2

A woman in her 20s presented with diffuse hair loss and thinning for 1 year. Trichoscopy revealed multiple broken and some corkscrew hairs (Figure 1B). Scalp biopsy showed noncicatricial alopecia with a normal anagen:telogen ratio (94%:6%) despite 32% of hair follicles exhibiting trichomalacia (Figure 2B). She later reported that she had used a detangling hairbrush for 6 months in the preceding year.

Case 3

A woman in her 30s presented with diffuse alopecia after detangling hairbrush use for more than 1 year. Trichoscopy and biopsy findings were similar to the previous patients (Figures 1C and 2C); 14% of hair follicles had trichomalacia, and the anagen:telogen ratio was normal (89%:11%).

In all cases, hair pull test, microscopy, and fungal element culture findings were negative. No perifollicular inflammation was seen on histology.

Discussion

All patients used detangling hairbrushes for at least 6 months before developing diffuse alopecia with acquired trichomalacia. Scalp biopsies revealed noncicatricial, noninflammatory alopecia, with hair follicles exhibiting features of trichomalacia (formation of a distorted hair shaft) in the absence of collapsed and obliterated follicular canals and relatively preserved anagen:telogen ratios.

Trichomalacia may occur in both trichotillomania and acute traction alopecia. However, collapsed inner root sheaths obliterating follicular canals, a feature of trichotillomania,¹ was not seen in these cases. Trichotillomania presents with decreased anagen:telogen ratios, but these were preserved in 2 cases. Diffuse alopecia distribution and absence of trichoscopic features such as hair casts, empty follicles, and loss of follicular openings pointed against a traction alopecia diagnosis.^2,3

We propose that this form of alopecia be called acquired diffuse trichomalacia (ADT). We postulate that traction from repeated detangling hairbrush use may cause unique tensile stresses on hair shafts and follicles, resulting in uneven transmission of mechanical forces through hair shafts, distortion of hair follicle matrix, interference with keratin deposition, and trichomalacia. Because hairbrush use was over the entire scalp, these defects were diffuse. Slow resolution of alopecia despite stopping hairbrush use may be due to the low-grade nature of the tensile stresses being insufficient to push hair into catagen to reset the hair cycle. Hence, the hair follicle remains in anagen and continues to produce a coiled, distorted hair shaft that breaks easily.

Interestingly, corkscrew hairs were seen. In a systematic review, corkscrew hairs had a 100% specificity and 98% positive predictive value for tinea capitis.⁴ Corkscrew hairs have not been reported as a feature of trichotillomania or traction alopecia.^3,5 Therefore, in patients with diffuse corkscrew hairs and negative fungal workup, ADT could be considered.

Management of ADT may be contingent on stopping culprit brush use. All patients in this series had persistent hair shaft defects and trichoscopic findings despite hairbrush cessation (2-12 months follow-up), suggesting that ADT may only resolve after passage of an entire hair cycle. Limitations of our study include small case numbers and lack of longitudinal data.

Supplement 1.

eFigure. Schematic Drawing of a Detangling Hairbrush

Supplement 2.

Data Sharing Statement