Reviews Looking past the lump: genetic aspects of inguinal hernia in children Christopher Barnett a , Jacob C. Langer b, ⁎ , Aleksander Hinek c , Timothy J. Bradley d , David Chitayat a a Division of Clinical and Metabolic Genetics, The Hospital for Sick Children, Toronto, Ontario, Canada b Division of General Surgery, The Hospital for Sick Children, Toronto, Ontario, Canada c Cardiovascular Research Laboratory, The Hospital for Sick Children, Toronto, Ontario, Canada d Division of Cardiology, The Hospital for Sick Children, Toronto, Ontario, Canada Received 28 November 2008; revised 18 December 2008; accepted 19 December 2008 Key words: Chromosomal abnormalities; Genetic syndromes; Indirect inguinal hernia; Direct inguinal hernia Abstract Inguinal hernia is associated with a multitude of genetic syndromes. Disorders of the microfibril, elastin, collagen, and the glycosaminoglycan component of the extracellular matrix can result in an increase in the likelihood of inguinal hernia. In addition, inguinal hernia may be the presenting feature of disorders of sexual differentiation. Inguinal hernia of unknown etiology also occurs more commonly in several other groups of genetic diseases including chromosomal disorders, microdeletion disorders such as 22q11.2 microdeletion, and in single gene disorders. We review the genetics of connective tissue formation and focus on a series of genetic conditions that may present with or are characterized by a higher risk of inguinal hernia. A comprehensive review of the literature aims to provide a diagnostic framework to aid in the identification of patients with inguinal hernia as part of underlying genetic disease. © 2009 Elsevier Inc. All rights reserved. Inguinal hernia repair is the commonest surgical procedure performed in childhood with an overall incidence ranging from 0.8% to 4.4% [1]. In most of cases in children, the hernia is indirect and primarily because of delayed closure of the processus vaginalis [2,3], although occasionally children may present with a direct hernia because of weakness of the muscular floor of the inguinal canal. The processus vaginalis is an invagination of the peritoneum through the internal ring that forms by the 12th week of gestation, becoming the tract by which the intraabdominal testis descends to the scrotum [4]. After successful testicular descent, the processus vaginalis usually obliterates above the descended testis. The mechanism of closure of the processus vaginalis remains poorly understood. If the processus vaginalis remains patent either after successful testicular descent or in association with an undescended testis, it provides a potential space for herniation of bowel or other organs into a hernial sac that may extend as far distally as the scrotum. In most cases, recurrence of a pediatric inguinal hernia is because of incomplete obliteration of the processus vaginalis during ⁎ Corresponding author. Robert M. Filler Chair of Pediatric General Surgery, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8. Tel.: +1 416 813 7340; fax: +1 416 813 7477. E-mail address: jacob.langer@sickkids.ca (J.C. Langer). www.elsevier.com/locate/jpedsurg 0022-3468/$ – see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.jpedsurg.2008.12.022 Journal of Pediatric Surgery (2009) 44, 1423–1431