Pili Annulati with Multiple Fragile Hairs.

Dear Editor:

A 25-year-old man visited Department of Dermatology, Dankook University Hospital with a complaint of whitish dots on his scalp hair that was coarse and broken easily. He noticed the changes for the first time about 6 years ago. He had used a hairdryer almost every day since he graduated high school. No family history except his father had androgenic alopecia. A physical examination revealed that the hair shafts were black mixed with alternating light brown color and multiple small white-gray spots were evident (Fig. 1A, B). On dermoscopic examination, the hair shafts had alternating light and dark bands with multiple white nodes (Fig. 1C). Light microscopy revealed an air-filled dark space or cavity, which appeared to be bright bands or white-gray beads on the hair shaft with the unaided eye (Fig. 1D). A scanning electron microscope showed loss of the cuticle, mild indentation and longitudinal fissuring on the hair shaft that revealed the microfibers of the cortex (Fig. 2A, B). In addition, white nodular swelling was evident that resembled the ends of two brushes aligned in opposition, and the end of the fractured hairs was a paint-brush appearance (Fig. 2C, D).

Fig. 1

(A) Regular alternating bright bands on hair shafts. (B) Multiple white-gray spots appearing like grains of sand exist on the hair shaft. (C) Alternating dark and bright bands with intermittent whit spots on the hair shaft appeared on the dermoscopic examination. (D) The air-filled dark spaces occupied 40%~80% of the hair shaft on inverted microscopy.

Fig. 2

(A) Loss of cuticle and mild indentation on the surface of mildly damaged hair. (B) Longitudinal cracks are visible in the hair shaft, which exposed the microfibers of the hair cortex. (C) Swollen node resembles two broomsticks pushed into each other and formed a so-called thrust paint brush. (D) Mechanical trauma on the swollen node fractured the hair ends, as shown by the frayed macrofibers.

Pili annulati (PA) has not been classically associated with increased hair fragility, as and tensile strength of hair in cases of PA is normal1. It has been suggested that intermittent hair banding without fragile hair may be related to a gene controlling hair growth dynamics instead of hair structure, such as keratins or keratin-associated proteins2. However, some abnormal weathering patterns have been reported in cases of PA, such as mild indentations to severe longitudinal folding in some hair shafts2345. Thus, the air filled spaces in cases of PA may be the reason for hair fragility, which would increase susceptibility to shearing stress4.

The scanning electron microscopic examination in our case revealed mild indentations or longitudinal cracking of the hair cortex, which is observed frequently in typical cases of PA. These findings could be the result of uneven compression of the hair shaft caused by the underlying air spaces4. Some severely damaged hair had multiple white nodes on the hair shaft or longitudinal fissures on the surface that exposed the microfibers of the cortex, which is usually observed in trichorrhexis nodosa. In particular, the nodes associated with the underlying air-filled cavities in a patient with PA may be the focus for the structural damage by environmental trauma4.

In conclusion, it is postulated that heavy use of hair dryer in our patient could have severely traumatized his underlying PA and caused multiple fragile hairs.