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Multiple Craniofacial Nodules and Plaques Distributed Bilaterally Along Blaschko Lines

Educational Objective
Based on this clinical scenario and the accompanying image, understand how to arrive at a correct diagnosis.
1 Credit CME

A male in his late teens presented with asymptomatic congenital papules, plaques, and nodules in a linear bilateral distribution following Blaschko lines on the scalp and face region. The papules and nodules appeared to grow as the boy grew, and some pedunculated lesions tended to fall off spontaneously. He had not received any prior treatment. The patient had no other significant medical history and denied having a family history of similar lesions. Clinical examination findings revealed multiple skin-colored, nontender soft papules of varying sizes protruding from the skin surface on the right cheek, forehead, and jaw, as well as on the anterior surface of the scalp, distributed along Blaschko lines, with sparse vellus hairs and multiple hair follicles on the lesions (Figure, A and B). However, no hair was observed on the lesion because the patient had shaved the hair on his face. An incisional biopsy of a pedunculated lesion above the left eyebrow was performed (Figure, B).

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A. Hair follicle nevus

Histological examination findings revealed densely populated well-formed vellus hairs with sebaceous glands and accentuation of the perifollicular fibrous sheath embedded in a fibrotic stroma (Figure, C and D). However, examination of multiple deeper sections did not reveal any additional components, such as cystic follicular structures, prominent adipose tissue, or cartilage (Figure, C and D). Hence, the lesion was diagnosed as a hair follicle nevus.

Hair follicle nevus is an extremely rare adnexal hamartoma with follicular differentiation.1 It is typically congenital and located on the face.1 Hamartomas are usually benign malformations composed of tissue elements normally found at that site, but grow in a disorganized fashion. However, some studies have shown that these lesions may occasionally undergo malignant degeneration. In fact, several chromosomal and genetic defects have been identified in benign neoplasms, hamartomas, and malignant tumors.24

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Article Information

Corresponding Author: Fang Yang, MD, PhD, Department of Dermatology, Shenzhen People’s Hospital (The Second Clinical Medical College, Jinan University, The First Affiliated Hospital, Southern University of Science and Technology), No. 1017, Dongmen North Rd, Luohu District, Shenzhen, 518020, Guangdong, China (yangfang3013@126.com).

Published Online: January 12, 2022. doi:10.1001/jamadermatol.2021.5474

Conflict of Interest Disclosures: None reported.

Disclaimer: The views expressed in this article are those of the authors and do not reflect the official policy of the Uniformed Services University, Department of the Army/Navy/Air Force, Department of Defense, or the government.

Additional Contributions: We thank the patient for granting permission to publish this information.

References
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Lee  JS , Yang  JH , Park  H , Yoon  HS , Cho  S .  Hair follicle nevus located on the neck: comparison with accessory tragus, cervical chondrocutaneous branchial remnants and trichofolliculoma.   Ann Dermatol. 2019;31(6):662-665. doi:10.5021/ad.2019.31.6.662 PubMedGoogle ScholarCrossref
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