Case report Nasal dermal sinus cysts with intracranial extension in a child mosaic for a supernumerary ring chromosome 20 Bernarda Lozic ´ a , Dras ˇko Cikojevic ´ b , Vlatko Ledenko c , Marisa Klanc ˇnik b , Ruz ˇica Lasan d , Tatijana Zemunik e, * a Department of Pediatrics, University Hospital Split, Spincˇic ´eva 1, 21000 Split, Croatia b Department of Othorinolaringology, University Hospital Split, Spincˇic ´eva 1, 21000 Split, Croatia c Department of Neurosurgery, University Hospital Split, Spincˇic ´eva 1, 21000 Split, Croatia d Department of Pediatrics, Clinical Hospital Centre Zagreb, Kisˇpatic ´eva 12, 10000 Zagreb, Croatia e Department of Medical Biology, University of Split, School of Medicine, S ˇ oltanska 2, 21000 Split, Croatia 1. Introduction The term nasal dermal sinus cyst (NDSC) includes all lesions containing ectoderm (stratified squamous epithelium) and meso- derm (adnexal structure) located in midline nasofrontal area [1]. Unlike other craniofacial dermoids, the nasal lesions can be presented as a cyst, a sinus, or a fistula and may have an intracranial extension [1]. Nasofrontal dermoid sinus cysts arise in the early embryonic development. Pathogenesis involves the incomplete obliteration of neuroectoderm in the process of frontonasal region development [2,3]. NDSCs are of ectodermal origin and occur as a result of failure in embryologic separation of neuroectodermal and ectodermal tissues [4]. The most widely accepted theory is based on Grunwald theory from 1910, later termed the prenasal theory by Pratt et al. and the cranial theory by Bradley et al. [2,5]. This theory is based on the finding that neuroectodermal tract retreats, and dermal attachments follow its course. When the dura mater retreats from the prenasal space back into the cranium, it may pull the nasal ectoderm upward and inward to form a sinus or a cyst [1]. The resulting epithelial lining forms a dermal sinus or cyst, depending on its connection to the nasal dorsal skin [6]. The distal opening of a dermal sinus may be found anywhere from the glabella to the columella [7]. Dermoids are usually midline, whereas epidenmoids occur mainly in the tip of the nose or slightly lateral to the nose. Meta-analysis showed that the incidence of NDSCs with intracranial communication was approximately 20% [8]. NDSCs have not been ascribed to any specific genetic defect. They have been associated with other congenital lesions, primarily with the lesions of first branchial arch, the congenital lesions of the face and brain that incidence ranges between 5 and 41% [1,9]. Wardinsky et al. assumed that presence of associated anomalies increases the probability of intracranial extension of a nasal dermoid [10]. NDSCs arise sporadically; however a familial association has been reported in the literature [11,12]. Supernumerary marker chromosome (SMC) including extra ring chromosomes occurs with a frequency of 0.14–0.72/1000 in newborns. The risk for phenotypic abnormalities associated with a marker chromosome depends on several factors such as inheri- tance, chromosomal origin, and the morphology, content, and structure of the marker [13,14]. The occurrence of an additional ring chromosome 20, r(20), is a rare chromosome abnormality and no common phenotype has been described yet [14]. International Journal of Pediatric Otorhinolaryngology Extra 7 (2012) 73–78 A R T I C L E I N F O Article history: Received 19 July 2011 Received in revised form 11 November 2011 Accepted 27 December 2011 Available online 26 January 2012 Keywords: Nasal dermal sinus cyst Intracranial extension Supernumerary ring chromosome 20 Frontonasal region Embryonic developmental error Surgical treatment A B S T R A C T Nasal dermal sinus cysts are congenital malformations that result from anomalous embryological development and are not prescribed to any specific genetic defect. The occurrence of a supernumerary ring 20 that causes a partial trisomy 20 mosaicism is a rare chromosome abnormality and no common phenotype has been described yet. We present a unique case of a 3.5-year-old child with a supernumerary ring chromosome 20 mosaicism associated with nasal dermoid with intracranial extension. It is possible that this genetic defect contribute to embryonic developmental errors of the frontonasal region. The clinical presentation, surgical treatment, and literature review of this case are discussed. ß 2012 Elsevier Ireland Ltd. All rights reserved. * Corresponding author. Tel.: +385 21 557 888; fax: +385 21 557 895. E-mail address: tzemunik@mefst.hr (T. Zemunik). Contents lists available at SciVerse ScienceDirect International Journal of Pediatric Otorhinolaryngology Extra jo ur n al ho m ep ag e: ww w.els evier .c om /lo cat e/ijp o r l 1871-4048/$ – see front matter ß 2012 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.pedex.2011.12.003