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The nevoid pili multigemini over the back

European Journal of Dermatology. Volume 15, Number 2, 99-101, March-April 2005, Clinical report

Summary

Author(s) : Joong Sun Lee, You Chan Kim, Hee Young Kang , Department of Dermatology, Ajou University School of Medicine, 5 Wonchon-Dong, Yeongtong-Gu, Suwon 443-721, Korea (South).

Summary : Pili multigemini is a rare developmental defect of hair follicles. It usually involves the beard of an adult and the scalp in children, but there have been no reported cases on the back. We report 3 cases of extensive pili multigemini over the entire back of healthy males. All cases were found incidentally. The direct microscopic examination of one hair follicle showed that it consisted of more than twenty shafts, which had rough surfaces and brush-like bulbs. The histological examination revealed that complicated follicular structures formed as many as 23 to even 36 hair shafts. Lots of hairs were surrounded by each inner root sheath and had one common outer root sheath. We suggest this nevoid is pili multigemini over the back.

Keywords : back, nevoid, pili multigemini

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ARTICLE

Auteur(s) :, Joong Sun Lee, You Chan Kim, Hee Young Kang^*

Department of Dermatology, Ajou University School of Medicine, 5 Wonchon-Dong, Yeongtong-Gu, Suwon 443-721, Korea (South)

accepté le 31 Août 2004

Pili multigemini is an unusual developmental defect of the hair follicles. This condition refers to multiple hair shafts arising from multiple divided matrices and papillae through a single pilary canal; each hair has its own inner root sheath and the hairs are surrounded by a common outer root sheath [1]. Pili multigemini was first described by Flemming (1883), who found a triplet hair in the beard skin. Multigeminate hairs have invariably been found in the beard of an adult and the scalp of children [2]. We found three cases of extensive pili multigemini involving the entire back of healthy males.

Case reports

Patient 1

A 27-year-old man visited for a skin lesion on the back. His friends found this lesion incidentally in the swimming pool. He had no subjective symptoms related with it and was otherwise healthy. The physical examination showed that there was a giant patch consisting of irregular and coarse thicker hairs over the entire back ( (figure 1A) ). Epilation did not require any considerable force and was not painful. The direct microscopic examination of one hair follicle showed that it consisted of more than twenty shafts, which had rough surfaces and brush-like bulbs (( figure 2 )). The histological examination of transverse sections revealed that complicated follicular structures formed as many as 23 to even 36 hair shafts which were enclosed in the common outer root sheath ( (figure 1A) ). There was eosinophilic material between the hair shafts and around the hair shaft. It suggested that each hair had its own inner root sheath. This was better visible in the section stained with Giemsa solution ( (figure 3) ). There was dark material between the hair shafts and around each shaft, which is Huxley’s layer stained deep blue.

Patient 2

A 60-year-old man who presented with generalized pruritus (( figure 1 )B). The physician accidentally found the pili multigemini over the back during the physical examination. The gross appearance of hair shafts and the histopathologic examination were similar with those of patient 1.

Patient 3

A 25-year-old man who presented with a stinging and itching sensation, on his whole body without skin lesions for about two years ( (figure 1C) ). The physical examination exposed pili multigemini over half of the back which was two to three times thicker than that of others, and folliculitis-like papules, macules are seen.

Discussion

The name ‘pili multigemini’ is used to define a kinetic papilla that splits at the upper end from a single to a multiple-tipped one during the anagen phase, producing eight or more different-sized hair shafts with separate cuticles and consequently the hair shaft does not fuse again [3]. The name ‘pili gemini’ is used when the dermal papilla splits into a double-tipped one and should be differentiated from pili bifurcati in which each branch is covered with its own cuticle. We showed that lots of hairs (23 or more) were surrounded by each cuticle and had one common outer root sheath, which was consistent with the diagnosis of pili multigemini. Trichostasis spinulosa, hyperkeratotic follicular papules, are characterized by the retention of numerous vellus hairs surrounded by a keratinous sheath in a dilated follicle, and can be easily differentiated from our case with clinical and histopathologic findings [4, 5].

The exact origin or mechanism of pili multigemini is still unknown. It was suggested that a subdivided papilla produced divided hairs, or multiple hairs may be due to the partial merging of several papillae, or that the reactivation of silent embryonic epithelial germs result in multigeminate hairs [1, 6]. Mehregan et al. [7] observed the regrowth of multigeminate follicles after the forced extraction of the hair shafts from one side of the chin. Thus they suggested that a fixed follicular malformation with the determining factor might reside within the area of the dermal papillae.

Pili multigemini may be localized, most commonly in the beard area of adults [2, 5, 8]. Our cases differ from other reported cases in that they occur over a large area, especially over the back. We think this nevoid multigeminate hair patch over the back would be a commonly recognizable condition with careful examination. In fact, in our patients the nevoid multiple hairs had no specific symptoms, and the lesion site is the back, as a result all cases were found by chance.

In conclusion, we report three cases of pili multigemini involving the entire back. Pili multigemini may occur on the back as well as the beard or the scalp and we suggest this nevoid is pili multigemini over the back.

References

1 Cambiaghi S, Barbareschi M, Cambiaghi G, et al. Scanning electron microscopy in the diagnosis of pili multigemini. Acta Derm Venereol 1995; 75: 170-1.

2 Price VH. Structural anomalies of the hair shaft. Pili multigemini. In: Orfanos CE, Happle R, eds. Hair and hair disease. Heiderlberg: Springer-Verlag, 1990: 414-5.

3 Camacho FM, Happle R, Tosti A, Whiting D. The different faces of pili bifurcate. A review. Eur J Dermatol 2000; 10: 337-40.

4 Strobos MA, Jonkman MF. Trichostasis spinulosa: itchy follicular papules in young adults. Int J Dermatol 2002; 41: 643-6.

5 Manuskiatti W, Tantikun N. Treatment of trichostasis spinulosa in skin phototypes III, IV, and V with an 800-nm pulsed diode laser. Dermatol Surg 2003; 29: 85-8.

6 Pinkus H. Multiple hairs (Flemming-Giovannini). Report of two cases of pili multigemini and discussion of some other anomalies of the pilary complex. J Invest Dermatol 1951; 17: 291-301.

7 Mehregan AH, Thompson WS. Pili multigemini. Report of a case in association with cleidocranial dysostosis. Br J Dermatol 1979; 100: 315-22.

8 Whiting DA. Hair shaft defects. Pili multigemini and pili bifurcati. In: Olsen EA, ed. Disorders of hair growth. Diagnosis and treatment. New York: McGraw-Hill, 1994: 118.