Dermatology: Practical and Conceptual


Image Letter | Dermatol Pract Concept. 2025;15(4):6116 1

Hair Collar Sign with Naevus Flammeus:  
A Possible Sign of Aplasia Cutis Congenita

Li Han1, Lang Rao1, Yong-bo Wu1, Yan-yi Deng2, Bo Luo3

1 Department of Dermatology, Chengdu Second People’s Hospital, Chengdu, Sichuan Province, China

2 School of Clinical Medicine, Chengdu Medical College, Chengdu, Sichuan Province, China

3 Department of Comprehensive Surgery Ward, Zigong Maternal and Child Health care Hospital, Zigong, Sichuan Province, China

Li Han and Lang Rao contributed equally to this work.

Citation: Han L, Rao L, Wu YB, Deng YY, Luo B. Hair Collar Sign with Naevus Flammeus: a Possible Sign of Aplasia Cutis Congenita. 
Dermatol Pract Concept. 2025;15(4):6116. DOI: https://doi.org/10.5826/dpc.1504a6116

Accepted: June 27, 2025; Published: October 2025

Copyright: ©2025 Han et al. This is an open-access article distributed under the terms of the Creative Commons Attribution-
NonCommercial License (BY-NC-4.0), https://creativecommons.org/licenses/by-nc/4.0/, which permits unrestricted noncommercial use, 
distribution, and reproduction in any medium, provided the original authors and source are credited.

Funding: None.

Competing Interests: None.

Authorship: All authors have contributed significantly to this publication.

Corresponding Author: Bo Luo, MM. No. 49 Dahuangtong Road, Longjing Street, Daan District, Zigong, Sichuan Province, 643021, 
China. E-mail: Noble910@163.com

Case Presentation

A 2-month-old female infant presented with a reddish patch 

and bald area on her scalp, which her parents had noticed 

one week earlier (Figure 1A). Dermoscopy revealed an atro-

phic patch lacking central follicular openings, surrounded 

by radiating coarser hairs and featuring thin linear, rounded, 

and globular vessels on a pinkish background (Figure 1B). 

She was diagnosed clinically with aplasia cutis congenita 

(ACC) with a hair collar sign (HCS) and naevus flammeus, 

supported by dermoscopic findings. Magnetic resonance im-

aging (MRI) demonstrated that the skull was closed and in-

tact, with normal intracranial structures (Figure 1C). She was 

advised to undergo close follow-up without intervention.

Teaching Point

Aplasia cutis congenita (ACC) is a rare congenital skin de-

fect that can occur anywhere on the body, most commonly 

on the scalp. A ring of coarser, darker hair surrounding a 

bald scalp lesion, termed HCS, is considered a specific clin-

ical sign of ACC. Prior studies suggest nearly half of HCS 

cases correlate with naevus flammeus (port-wine stains); 

this association may arise from aberrant migration of neu-

ral crest cells affecting fetal skin development, particularly 

in capillary network formation [1]. In ACC cases, because 

the presence of HCS and vascular stains are considered as a 

marker for neuroectodermal defects (e.g., heterotopic brain 

tissue or cephalocele), an MRI is essential for evaluation [2].

In conclusion, HCS is frequently associated with naevus 

flammeus and may indicate aplasia cutis congenita. Patients 

demonstrating this cutaneous marker should undergo thor-

ough physical examination coupled with MRI evaluation of 

the craniospinal axis.

Ethical Statement: Written informed consent was obtained 

from the patient’s parents for publication of this case letter 

and any accompanying anonymized data/images. The par-

ents were informed that all personal identifiers would be re-

moved to protect privacy.



2 Review | Image Letter Pract Concept. 2025;15(4):6116

Acknowledgement: We thank the patient’s parents for grant-

ing permission to publish this information.

References

1. Marneros AG. Aplasia Cutis Congenita Pathomechanisms Reveal 

Key Regulators of Skin and Skin Appendage Morphogenesis.  

J Invest Dermatol. 2024;144(11):2399-2405. DOI:10.1016/j 

.jid.2024.05.014. PMID: 39023472.

Figure 1. (A) A reddish patch with a hair collar sign is present on the occipital region of an infant; (B) Dermoscopy 

revealed an atrophic patch surrounded by radiating hair follicles, with thin linear, rounded, and globular vessels on a 

pinkish background (polarized 30x); (C) MRI scan showed the skull was intact, with normal intracranial structures.

2. Bessis D, Bigorre M, Malissen N, et al. The scalp hair col-

lar and tuft signs: A retrospective multicenter study of 78 pa-

tients with a systematic review of the literature.  J Am Acad  

Dermatol. 2017;76(3):478-487. DOI:10.1016/j.jaad.2016.08.046.  

PMID: 27742172