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Year : 2012  |  Volume : 4  |  Issue : 2  |  Page : 89-92  

Pili annulati with fragility: Electron microscopic findings of a case

1 Dermatology Clinic, Ankara Ataturk Training and Research Hospital, Ankara, Turkey
2 Department of Anatomy, Hacettepe University Faculty of Medicine, Ankara, Turkey

Date of Web Publication1-Jun-2012

Correspondence Address:
Gulsen Akoglu
Dermatology Clinic, Ataturk Training and Research Hospital, Bilkent, Ankara
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0974-7753.96909

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Pili annulati (PA) is typically characterized by shinny beads seen along the hair shaft. PA is accepted to belong to the classification of hair shaft abnormalities without fragility. Herein, we described a 14-year-old, fair skin with dark-haired girl diagnosed as PA with fragility which was demonstrated by weathering features in electron microscopic examinations. The patient had shinny beaded, easily breakable hairs since the age of four. A few broken hairs were observed by a light pull test. Transmitted light microscopy revealed periodic dark bands in the hair shaft. These dark bands disappeared after application of 10% aqueous potassium hydroxide. Multiple cavities within hair shaft and severe cuticular damages representing the weathering pattern were observed in electron microscopic examinations. All these findings were found to be consistent with presence of fragility in PA. This case provides evidences of fragile hair structure of PA which may be due to pathological cavities within hair shafts.

Keywords: Electron microscopy, fragility, hair shaft abnormality, pili annulati, shinny beads, weathering pattern

How to cite this article:
Akoglu G, Emre S, Metin A, Erbil K M, Akpolat D, Firat A, Hayran M. Pili annulati with fragility: Electron microscopic findings of a case. Int J Trichol 2012;4:89-92

How to cite this URL:
Akoglu G, Emre S, Metin A, Erbil K M, Akpolat D, Firat A, Hayran M. Pili annulati with fragility: Electron microscopic findings of a case. Int J Trichol [serial online] 2012 [cited 2023 Jun 3];4:89-92. Available from: https://www.ijtrichology.com/text.asp?2012/4/2/89/96909

   Introduction Top

Pili annulati (PA) is a rare hair shaft abnormality, characterized by shinny beads seen along the hair shaft. These beads reversely correspond to the alternating dark bands among light bands under transmitted light microscopy. [1] Since PA was first described by Landois in 1866, [1] only about 50 cases with PA has been published. The pathogenesis of PA has not been clearly established yet. PA is considered to be autosomal dominantly inherited hair shaft disorder, but sporadic cases have also been reported. [2] It can present at birth, during infancy, or after age of two. PA may be firstly obvious after puberty or in adulthood. [3],[4] Although the scalp has been mostly reported to be affected, pubic, [5] beard, [6] and axillary hairs [7] have been also reported to be involved. The abnormalities of PA become more noticeable with age, in contrast to fragility-associated disorders, in which fragility becomes subtle with puberty. [8]

Although PA was categorized in hair shaft abnormalities without fragility, two patients were shown to have fragile hairs corresponding to weathered hair structure due to internal weakness of the shaft caused by pathological cavities. [9] In this report, we described a girl diagnosed as PA with fragility and demonstrated the weathering features in electron microscopic examinations. This case provides additional evidences of fragile hair structure of PA which were suggested in only a small number of patients.

   Case Report Top

A 14-year-old, fair skinned, dark-haired Causation girl was presented with shinny beaded, easily breakable hairs since she was four [Figure 1]. Hairs were only cosmetically disturbing for the patient and her family. There was no history of any trauma, shedding, or alopecia. Her parents were nonconsanguineous. Her mother had had similar hairs during her childhood and adolescence, which improved as she got older. The other family members were not available for examination. The axillary and pubic hairs were normal. On examination, a few broken hairs came to hand by a light pull test. Transmitted light microscopy revealed periodic dark bands in the hair shaft [Figure 2], which diminished toward to the end of hair. The otherwise dermatological and systemic examinations were normal.
Figure 1: Shinny beading along the hair shafts

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Figure 2: Periodic dark bands in the hair shaft under transmitted light microscopy

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Under light microscopy, the hair samples within normal medium [Figure 3]a were then embedded in 10% aqueous potassium hydroxide. The dark bands disappeared after 6 minutes and homogeneous color along hair shaft was achieved [Figure 3]b. Upon this observation, these bands were considered as pathological cavities in hair structure, not normal medulla bands.
Figure 3: (a) Dark cavities seen within normal medium disappeared (b) after 6 minutes of embedding in 10% aqueous potassium hydroxide medium under light microscopy

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To perform electron microscopic examinations, the hair samples of the patient were mounted on stubs and sputter coated with gold paladium. Then they were examined with a scanning and transmission electron microscope (JEM 1200EX, Jeol, Tokyo, Japan). Transmission electron microscopy (TEM) of the hair samples demonstrated various sizes of multiple cavities within cuticular and cortical cells and indentations adjacent to these cavities [Figure 4]a and b. Scanning electron microscopic examination (SEM) provided observations of various severe cuticular damages corresponding to the localizations of cavities [Figure 5]a-d. In contrast, the unaffected hairs had normal hair structure.
Figure 4: Transmission electron microscopy showed (a) multiple cavities between cuticular and cortical cells and (b) indentations of undamaged cuticle adjacent to cavities (arrowed)

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Figure 5: a-d: Scanning electron micrographs of hair samples demonstrated damaged cuticle and cortex structures with various severities of changes adjacent to pathological cavities within hair shafts

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Depending on these clinical features and light and electron microscopic findings, the patient was diagnosed as PA with fragility and weathered structure.

   Discussion Top

PA is clinically more noticeable in fair hairs than dark-haired patients as in this case, because less pigmented hairs transmit more light in transmitted light microscopy. [1] Light bands seen with naked eye were suggested to correspond to air-filled spaces [10] or proteinaceous materials. [1] They do not transmit the light under light microscopy and appear as dark pathological cavities located in the cortex of hair shaft that scatter the light. [5] The pigmented medulla should be differentiated since they may resemble dark bands when it is present intermittently. Medulla has rounded tips in contrast to tapering and sharp cavities in PA. [3] The disappearance of dark bands in 10% aqueous potassium hydroxide medium may be used to support the diagnosis of PA. The cuticular damage in PA hairs might have allowed the penetration of the medium into cavities or collapsing of the cavities leading the transmission of the light. [11]

Pseudopili annulati (PPA) is the main differential diagnosis for PA. It is a type of ringed hair with beads appearing upon transverse illumination because of the elliptical shape and twisting of the hair. The hair shaft of PPA is normal under transmitted light microscopy, TEM, and SEM, in contrast to PA. The hair fiber appears uniformly dark without banding; however, it shows variations in thickness causing repeated fusiform segments. PPA has not been shown to be related to any inheritance or associated with any other abnormality, unlike PA. [12] As seen in our case, clinical findings and light microscopic features did not demonstrate features of PPA.

The pathogenesis of PA has been explained depending on several mechanisms such as an underlying cytokeratin abnormality [1] or a matrix formation defect. [11] Several basal membrane zone components were demonstrated to be abnormally distributed. [2] A mutation in proteins involved in signaling and regulation of formation and degradation of the lamina densa and sublamina densa region might result in an abnormal assembly or remodeling of the basal membrane zone. PA was found unlikely to be attributable to an abnormality of any of the common known cytokeratins examined. [10] In 2004, a gene locus responsible for PA was mapped to chromosome 12q24.32-24.33. Because chromosome 12q locus does not contain structural genes related to the keratin genes, it is more likely that PA may be caused by a mutation in a regulatory gene affecting hair follicle cell proliferation or differentiation. [3]

The aminoacids of the hairs with PA demonstrated elevated lysine and decreased cysteine content. These findings may be parts of the responsible process contribute to fragility that has been suggested in some patients with PA, [11] although hair fragility has not been mentioned as a clinical feature of PA. [13] It is well known that abnormal hair structures are prone to excessive weathering than normal hair shafts due to underlying cavities within cortex leading to intrinsic shaft weakness. In SEM, the cuticle of the affected hair may seem to be intact but it has a cobblestoned appearance and fluted. Because of the multiple cavities within and around cortical cells, the cuticular cells may be thrown into these folds. In TEM, many abnormal cavities of varying spaces and sizes are observed within the cortex between cortical macrofibrils and within cortical cells. Beside these alterations, medulla remains intact and normal. [9] The electron microscopic findings of our patient were compatible with these features of PA. Besides, SEM demonstrated rare findings of weathering seen in PA as described in the report of Feldmann et al. [9] The nodes of PA might have weakened hair structure and breaks when exposed to physical trauma such as vigorous combing and environmental factors. Minor indentations as in our case might not cause breaks in hair shaft.

Although quantitative examinations of tensile breaking strength were within normal limits, vigorous combing, brushing of the hair, or cosmetic measures result in excessive weathering and structural damage associated with these pathological nodes in PA. Therefore, avoiding physical trauma, vigorous combing, cosmetic implementations were recommended to the present case to reduce fragility.

In conclusion, the diagnosis of PA needs careful clinical and microscopic examinations since it is asymptomatic and clinically less apparent in time. Although PA is generally classified in hair shaft disorders without fragility, some patients may have fragility due to pathological cavities within hair shafts.

   References Top

1.Gummer CL, Dawber RP. Pili annulati: electron histochemical studies on affected hairs. Br J Dermatol 1981;105:303-9.  Back to cited text no. 1
2.Giehl KA, Ferguson DJ, Dean D, Chuang YH, Allen J, Berker DA, et al. Alterations in the basement membrane zone in pili annulati hair follicles as demonstrated by electron microscopy and immunohistochemistry. Br J Dermatol 2004;150:722-7.   Back to cited text no. 2
3.Green J, Fitzpatrick E, de Berker D, Forrest SM, Sinclair RD. A gene for pili annulati maps to the telomeric region of chromosome 12q. J Invest Dermatol 2004;123:1070-2.   Back to cited text no. 3
4.Green J, Sinclair RD, de Berker D, Sinclair RD. Disappearance of pili annulati following an episode of alopecia areata. Clin Exp Dermatol 2002;27:458-60.   Back to cited text no. 4
5.Amichai B, Grunwald MH, Halevy S. Hair abnormality present since childhood. Pili annulati. Arch Dermatol 1996;132:575,8.  Back to cited text no. 5
6.Musso LA. Pili annulati. Australas J Dermatol 1970;11:67-75.  Back to cited text no. 6
7.Montgomery RM, Binder AI. Ringed hair. Arch Dermatol Syphilol 1970;58:177-9.  Back to cited text no. 7
8.Moffitt DL, Lear JT, de Berker DA, Peachey RD. Pili annulati coincident with alopecia areata. Pediatr.Dermatol 1998;15:271-3.  Back to cited text no. 8
9.Feldmann KA, Dawber RP, Pittelkow MR, Ferguson DJ. Newly described weathering pattern in pili annulati hair shafts: a scanning electron microscopic study. J Am Acad Dermatol 2001;45:625-7.  Back to cited text no. 9
10.Giehl KA, Dean D, Dawber RP, Leigh I, de Berker DA, Wojnarowska F. Cytokeratin expression in pili annulati hair follicles. Clin Exp Dermatol 2005;30:426-8.  Back to cited text no. 10
11.Giehl KA, Ferguson DJ, Dawber RP, Pittelkow MR, Foehles J, de Berker DA. Update on detection morphology and fragility in pili annulati in three kindreds. J Eur Acad Dermatol 2004;18:654-8.  Back to cited text no. 11
12.Lee SS, Lee YS, Giam YC. Pseudopili annulati in a dark-haired individual: A light and electron microscopic study. Pediatr Dermatol 2001;18:27-30.  Back to cited text no. 12
13.Price VH. Structural anomalies of the hair shaft. In: Orfanos CE, Happle R, editors. Hair and hair diseases. New York: Springer-Verlag; 1990. pp. 363-422.  Back to cited text no. 13


  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]

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