The hair collar sign - a possible indication of cranial dysraphism

Nevus Sebaceus Arising Within a Scalp Whorl of a Healthy Male Neonate

Nevus sebaceus (NS) and scalp whorl are both benign congenital findings that have not previously been reported to occur simultaneously. In most cases, the isolated finding of a single, classic-appearing NS or a single hair whorl can be followed clinically with observation. However, the number of lesions, distribution, and size of NS along with atypical placement of a scalp hair whorl can indicate an underlying syndrome or even underlying cranial abnormalities. We present a unique case of NS arising within a hair whorl on the vertex scalp of an otherwise healthy male neonate. After ultrasound showed no vascular malformations or proliferations and no cranial extension at the site, the lesion was later treated with surgical excision at six months old per the parents' preference, thus allowing for histologic confirmation of NS. Additionally, we discuss herein the diagnostic implications, recommendations for work-up, and treatment options of NS.

Membranous aplasia cutis congenita in trisomy 18

BACKGROUND

Aplasia cutis congenita (ACC) is a rare congenital condition characterized by the absence of skin layers and sometimes other underlying structures, in a localized or widespread area. The exact etiopathogenesis is not yet completely understood. Membranous ACC (MACC) also described as bullous or cystic ACC is a clinical subtype of ACC, covered with a membranous or glistening surface, and appears as a flat scar. There are less than 20 cases reported in the literature. It has been proposed an abortive form of a defective closure of the neural tube. On the other hand, the trisomy 18 is a chromosomal abnormality characterized by a broad clinical spectrum and the presence of defective closure of the neural tube.

CASE PRESENTATION

We report on an 18-months-old Venezuelan boy, who presented on the parietal scalp a distinctive localized MACC appearing as an oval lesion covered with a membranous surface, characterized by the absence of hairs and the presence of a sharp hair collar. The karyotype in peripheral blood was 47,XY,+ 18.

CONCLUSIONS

This is the second case report of ACC in trisomy 18 and reinforces the interpretation of a non-fortuitous association as well as of a defective closure of the neural tube as pathogenetic mechanism. The case highlights the importance of examining for dermatological alterations such as ACC in cases of chromosomopathy.

[Developmental abnormalities and nevi of the scalp]

Unusual congenital or early-onset skin lesions on the scalp often pose a diagnostic challenge particularly as the clinical evaluation may be hampered by dense hair growth. Thus, this paper provides a concise review on developmental abnormalities and nevi with exclusive or predominant scalp localization. Aplasia cutis congenita occurs as an isolated finding, in association with genetic syndromes, nevi and anomalies or as a consequence of intrauterine trauma and teratogens. A hairless area with a narrow surrounding rim of hypertrichosis (hair collar sign) may point to occult cranial dysraphism, especially if accompanied by further suggestive signs as port-wine stains, large hemangiomas, dimples, congenital dermoid cysts, and sinuses. Many diverse entities may hide behind cutis verticis gyrata with the primary essential form being rare and representing a diagnosis of exclusion. In contrast to former belief, benign adnexal tumors arise in a nevus sebaceus considerably more often than basal cell carcinomas and other malignant epithelial tumors. Provided that tumor development is not suspected, excision of a nevus sebaceus nevus is indicated primarily for aesthetic-psychosocial reasons. However, surgical treatment is considerably easier in small children. Nevus sebaceus may be a cutaneous marker for several complex syndromes whereas nevus psiloliparus presents almost always in connection with encephalocraniocutaneous lipomatosis. Congenital melanocytic nevi of the scalp tend toward clinical regression, so that surgical intervention in large lesions should be carefully considered. In contrast, the threshold for excision of blue nevi and other conspicuous melanocytic nevi on the scalp should be low, especially since they are difficult to monitor.