Eruptive Vellus Hair Cysts Manifesting as Type 1 Segmental Mosaicism
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Letter to the Editor
P: 23-23
March 2024

Eruptive Vellus Hair Cysts Manifesting as Type 1 Segmental Mosaicism

Turk J Dermatol 2024;18(1):23-23
1. Department of Dermatology, James Paget University Hospital, Great Yarmouth, United Kingdom
No information available.
No information available
Received Date: 20.03.2023
Accepted Date: 31.12.2023
Publish Date: 20.05.2024
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Dear Editor,

I read with interest the outstanding case recently published in the Turkish Journal of Dermatology.1 Poddar et al.1 reported eruptive vellus hair cysts (EVHC) arranged in a segmental distribution, namely in S-shaped bands respecting the midline. The authors define such a pattern as “zosteriform”. Instead, the lesions seem to clearly follow Blaschko lines, which are a known phenotypical pattern of cutaneous mosaicism and the only one followed by mosaic conditions affecting the pilosebaceous unit (e.g. nevus comedonicus). Only two cases of lateralized EVHC have been reported previously,2,3 but their distribution of lesions is not compatible with segmental mosaicism. Hence, this is the first reported instance of mosaic EVHC.

EVHC can arise sporadically or may be inherited in an autosomal dominant fashion with incomplete penetrance;4 the genetic defect has not yet been identified. In autosomal dominant skin disorders, heterozygosity for a postzygotic new mutation is defined as type 1 segmental mosaicism.5 Hence, the case of Poddar et al.1 allows the inclusion of EVHC among the ever-growing list of conditions known to possibly manifest as type 1 segmental mosaicism.

References

1
Poddar S, Gayen T, Chatterjee G. Zosteriform eruptive vellus hair cyst: A rare entity with an uncommon presentation. Turk J Dermatol 2022;16:98-100.
2
Lew BL, Lee MH, Haw CR. Unilateral eruptive vellus hair cysts occurring on the face. J Eur Acad Dermatol Venereol 2006;20:1314-1316.
3
Almutairi A, Elkhashlan M, Zeitony S. Eruptive vellus hair cysts: A localized unilateral variant. Gulf J Dermatol Venereol 2016;23:45-49.
4
Torchia D, Vega J, Schachner LA. Eruptive vellus hair cysts: a systematic review. Am J Clin Dermatol 2012;13:19-28.
5
Happle R. The categories of cutaneous mosaicism: A proposed classification. Am J Med Genet A 2016;170A:452-459.
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