Pedunculated lesion of the scalp with surrounding long, dark hair in a newborn. Nevus sebaceus of Jadassohn with the hair collar sign

Cerebriform sebaceous nevus: a subtype of organoid nevus due to specific postzygotic FGFR2 mutations

BACKGROUND

Postzygotic mutations in FGFR2 have been identified in mosaic forms of acne, keratinocytic epidermal nevi, nevoid acanthosis nigricans / rounded and velvety epidermal nevus and in two fetuses with papillomatous pedunculated sebaceous nevus (PPSN).

OBJECTIVES

To determine the clinical and genetic characteristics of children with cerebriform, papillomatous and pedunculated variants of sebaceous nevi.

METHODS

Infants diagnosed with sebaceous nevi characterized by a cerebriform, papillomatous and/or pedunculated morphology over a 10-year period (2010-2019) at three paediatric dermatology centres in Switzerland and France were included in this case series. Clinical and histological characteristics were assessed. Next-generation sequencing was used to assess for FGFR2 mutations.

RESULTS

All nevi were located on the head, with a rounded or linear shape and a typical cerebriform, sometimes papillomatous and pedunculated, surface. No associated extracutaneous anomalies were found. Nevi harboured postzygotic mutations in the transmembrane domain of FGFR2 in 6/8 children (75%), either the known specific p.(Cys382Arg) mutation in 5 cases, or a novel mutation, p.(Val395Asp), in one.

CONCLUSIONS

We found an exquisite genotype-phenotype correlation in these rare nevi, with specific postzygotic mutations in the transmembrane domain of FGFR2. As not all lesions were truly papillomatous and pedunculated, the term cerebriform sebaceous nevus (CSN) appears more suitable than PPSN to describe this entity. The cerebriform pattern of CSN is reminiscent of cutis gyrata, as seen in Beare-Stevenson syndrome, which is caused by closely related germline FGFR2 mutations. While clinically impressive, CSN seem to carry a good prognosis and a low risk for extracutaneous associations.

The scalp hair collar and tuft signs: A retrospective multicenter study of 78 patients with a systematic review of the literature

BACKGROUND

Hair collar sign (HCS) and hair tuft of the scalp (HTS) are cutaneous signs of an underlying neuroectodermal defect, but most available data are based on case reports.

OBJECTIVE

We sought to define the clinical spectrum of HCS and HTS, clarify the risk for underlying neurovascular anomalies, and provide imaging recommendations.

METHODS

A 10-year multicenter retrospective and prospective analysis of clinical, radiologic, and histopathologic features of HCS and HTS in pediatric patients was performed.

RESULTS

Of the 78 patients included in the study, 56 underwent cranial and brain imaging. Twenty-three of the 56 patients (41%) had abnormal findings, including the following: (1) cranial/bone defect (30.4%), with direct communication with the central nervous system in 28.6%; (2) venous malformations (25%); or (3) central nervous system abnormalities (12.5%). Meningeal heterotopia in 34.6% (9/26) was the most common neuroectodermal association. Sinus pericranii, paraganglioma, and combined nevus were also identified.

LIMITATIONS

The partial retrospective design and predominant recruitment from the dermatology department are limitations of this study.

CONCLUSIONS

Infants with HCS or HTS are at high risk for underlying neurovascular anomalies. Magnetic resonance imaging scans should be performed in order to refer the infant to the appropriate specialist for management.