Hair Growth Around the Scar. Potential Therapeutic Modality to Treat Alopecias?

Sir,

Injury to the tissue stimulates various factors for regeneration of the epidermis and its appendages and rarely induces the growth of new hair follicles. We report a case of an 18-year-old male who presented with new hair growth around the sites of trauma, potentially giving a concept of inducing hair growth.

An 18-year-old young boy sustained trauma to his chin at the age of 16 years, which was sutured. He noticed hair growth around the suture line 1 year later, around the time of appearance of moustache. Three months ago, he developed a spontaneous, painless, swelling along the right mandible, which was excised. Details of the nature of the swelling were not available. However, within 2 months, he again developed a firm painless swelling at the same site, but it was accompanied by hair growth along the previous suture line. There was no history of any topical or intralesional treatment such as steroids at the local site. Interestingly, the patient also had a history of inability to grow a beard in self, older brother, and father, which further made the growth of this hair around the scar more apparent.

On examination, there was a single atrophic linear scar of length 3 cm with 3 suture lines perpendicular to it. Coarse terminal hair was seen around the scars but not over the scar surface [Figure 1]. The patient also had a single, well-defined, firm, skin-colored, oval swelling of size 2.5 cm × 0.5 cm present along the right mandible, approximately 3 cm away from the angle of the mandible. Similar coarse terminal hair was seen surrounding it sparing the surface [Figure 1]. Histopathological examination of this swelling showed thick, well-organized collagen bundles in the dermis, and the features were consistent with a hypertrophic scar. Hormonal evaluation (serum testosterone, prolactin, and DHEAS) was within the normal limits.

Figure 1

Terminal hair around the atrophic as well as hypertrophic scar

Neogenesis of hair follicles around scars or trauma sites is an interesting phenomenon. Localized hypertrichosis as seen in our case has been mentioned secondary to multiple trigger factors compiled in Table 1.[12]

Table 1

List of the potential triggering factors for the stimulation of hair growth

Potential triggers for hair growth

1) Healing fractures

2) Pressure

3) Repetitive friction

4) Periphery of burns

5) Insect bites

6) Intermittent pressure

7) Vaccines like smallpox, BCG, tetanus, diphtheria

8) Osteomyelitis

9) Gonococcal arthritis

10) Chickenpox

11) Soft-tissue infections

The exact pathogenesis is still unclear, but multiple hypotheses have been proposed to justify the phenomenon. Regenerating epidermis might be the key for neogenesis of hair follicle under the influence of complex interplay between the receptors and growth factors. Wnt signaling, platelet-derived growth factor-A, hepatocyte growth factor (HGF), insulin-like growth factor-1(IGF-1), fibroblast growth factor (FGF), and noggin (bone morphogenetic protein inhibitor) are well-established signals for the neogenesis and morphogenesis of the hair follicles that have also been observed in in vitro studies of follicle regeneration.[3] Authors have also suggested that transient vanilloid receptor-1 (TRV-1) stimulated by heat or inflammation may also induce an anagen phase even in the telogen hairs.[4] High-mobility group box 1 (HMGB1) is another unique nuclear protein that is released from the cellular nuclei following cellular injury or trauma. It stimulates the elongation of the hair follicle in ex vivo studies by triggering the mRNA expression, thereby increasing the production of prostaglandin E synthases in the human dermal papillae cells.[5]

Our patient had a familial history of inability to grow a beard, which helped us to point out the presence of this hair around the hypertrophic and atrophic scars. Understanding the exact mechanism may help to unveil a new potential therapeutic option for the treatment of alopecia. However, a controlled trauma producing the hair growth without causing scarring is the desired outcome.

Take home message: Therapeutic wounding may trigger hair growth.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.