Pili Annulati in a Black-Haired Asian Woman

Abstract

Pili annulati (PA) is a rare autosomal dominant hair shaft disorder characterized by alternating light and dark bands along the hair shaft. It is more commonly observed in individuals with blond or light-colored hair, while cases in patients with dark hair are uncommon, as the greater amount of hair pigment can obscure the banding pattern, making it more difficult to recognize. As a valuable adjunctive tool, dermoscopy is valuable for revealing the characteristic features of PA, including alternating bright and dark bands along the hair shaft, sometimes accompanied by multiple white nodes. Here, we report a case of PA in a black-haired Asian woman with a 30-year history. Dermoscopy revealed the typical banding pattern, but notably, no obvious white nodes were observed. The positive family history further supports the familial nature of PA, although it alone is insufficient to establish an autosomal dominant inheritance pattern.

Introduction

PA is an uncommon hair shaft abnormality with an autosomal dominant inheritance pattern. The hallmark clinical feature is the presence of alternating white and normal-colored hair bands, giving the hair a “zebra stripe” appearance.^1,2 Because additional pigment in dark-colored hair can obscure the banding pattern, PA is more commonly reported in blond or light-colored hair.³ Two cases of Asian patients with black hair have been reported, including a Korean adult patient and a Chinese pediatric patient, in whom dermoscopy facilitated the recognition of the characteristic banding pattern. However, their dermoscopic findings differed in the presence of nodes: multiple white nodes were observed along the hair shafts in the Korean patient, whereas no obvious nodes were identified in the Chinese patient.^2,4 Our case of a black-haired Asian woman provides additional insight into the phenotypic variability of this condition.

Case Report

A32-year-old Asian womanwith a30-year history of multiple white spots on her scalp hair. The white spots had been present since childhood and could not be removed by washing, combing, or scraping. She denied scalp pruritus or pain but noted that hair breakage occasionally occurred at the sites of these white spots. Her past medical history was unremarkable, with no history of alopecia areata, diabetes mellitus, or thyroid disease. She had never dyed or chemically treated her hair. The patient also reported that neither parent nor offspring had similar symptoms, but one of her two elder sisters was also affected.

Dermatological examination revealed hair shafts of normal diameter without twisting or nodularity. Some shafts showed minimal adherent scales. More than 50% of the hairs displayed intermittent white bands measuring 0.5–1.0 mm in length, giving her hair a shiny, speckled appearance (Figure 1). No alopecic patches were noted, and the affected hairs did not show increased fragility on gentle hair pull testing. Dermoscopy demonstrated alternating bright and dark bands along the hair shaft (Figure 2A). The bright bands were cloud-like and extended across the entire shaft diameter (Figure 2B). No shaft nodules or fractures were observed. These findings were consistent with PA. The patient was informed of the benign nature of the condition and advised to avoid chemical or thermal hair treatments that could exacerbate shaft fragility. No specific therapy was initiated.

Figure 1.

Gross view showing multiple white speckles along the scalp hair, producing a shiny appearance.

Figure 2.

Dermoscopy (×10) revealing alternating light and dark bands (A). Dermoscopy (×50) showing cloud-like bright bands with ill-defined borders spanning the full hair shaft diameter (B).

Discussion

PA is a structural hair shaft disorder resulting from air-filled cavities within the cortex that alter light reflection, producing the characteristic banding pattern.⁵ These changes generally do not impair hair growth or cause significant fragility, but they may reduce tensile strength,⁶ which explains the occasional breakage reported by our patient.

Although PA is typically an isolated finding, some reports have suggested possible associations with alopecia areata, autoimmune thyroid disease, and selective IgA deficiency.¹ In our case, no systemic or autoimmune comorbidities were detected. PA is an autosomal dominant disorder, with a variable expression, but sporadic cases have also beendescribed.⁷ The presence of similar findings in the patient’s elder sister is consistent with the previously reported autosomal dominant inheritance pattern, while the absence of clinically apparent findings in the parents may reflect the variable expression of PA. However, genetic testing was not performed in our case, and therefore the inheritance pattern in this family cannot be definitively established.

Across these reported cases, the alternating bright and dark banding pattern appears to be the most consistent dermoscopic feature of PA. However, the morphology of the light bands may vary. In the Korean case, the alternating bands were accompanied by multiple white nodes,⁴ whereas neither our patient nor the previously reported Chinese pediatric case showed associated nodules.² These differences may reflect variations in the distribution and extent of the underlying air-filled cavities within the hair cortex and further expand the spectrum of dermoscopic features of PA.

The main differential diagnoses of PA include pseudopili annulati, bubble hair deformity, and monilethrix. Pseudopili annulati arises from partial twisting of the hair shaft with light reflection and usually lacks a family history.⁶ Bubble hair deformity arises from heat-induced vaporization of water within the hair shaft, leading to bubble formation and increased fragility.⁸ Monilethrixis characterized by uniform elliptical nodes separated by internodal constrictions; affected hairs rarely grow longer than 1–2 cm and break easily at the constrictions.³ In contrast, our patient’s findings of band-like bright segments, absence of nodularity, and positive family history strongly supported the diagnosis of PA.

Currently, no specific therapy for PA is available. Since the condition is benign and usually does not affect quality of life, management focuses on patient reassurance and avoidance of chemical or thermal insults to the hair.

The main limitations of this case are the absence of light microscopy, electron microscopy, and genetic testing. Although these investigations were not essential for diagnosis, they could have provided further insights into the ultrastructural and genetic characteristics of PA. In addition, direct clinical examination of the affected sister was not performed, and long-term follow-up was unavailable.

Conclusion

In conclusion, we describe a case of PA in a black-haired Asian woman with a positive family history. The characteristic alternating bright and dark bands along the hair shaft on gross examination, together with the more clearly visualizedbanding pattern on dermoscopy, are key diagnostic features. Dermoscopy is particularly valuable as it can increase diagnostic confidence and help avoid unnecessary investigations.

Consent

Written informed consent was obtained from the patient for the publication of this case report and any accompanying images. Institutional approval was not required for this case study.

Disclosure

The authors report no conflicts of interest related to this work.