Gardner syndrome describes a variant phenotype of familial adenomatous polyposis (FAP), primarily characterized by extracolonic lesions including osteomas, dental abnormalities, epidermal cysts, and soft tissue tumors. We describe a 2-yr-old boy presenting with a 2-cm soft tissue mass of the forehead. Pathologic evaluation revealed a nuchal-type/ Gardner-associated fibroma. Sequencing of the APC gene revealed a pathologic variant c.4666dupA. Parental sequencing of both blood and buccal tissue supported the de novo occurrence of this pathologic variant. Further imaging revealed a number of additional lesions including a large lumbar paraspinal desmoid, a 1-cm palpable lesion posterior to the left knee, firm lesions on bilateral heels, and multiple subdermal lesions. Colonoscopy was negative. This case illustrates a genetic variant of Gardner syndrome resulting in an aggressive early childhood phenotype and highlights the need for an individualized approach to treatment.
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Interestingly, dysfunction of the Wnt-β catenin pathway and abnormalities of cilia development have been hypothesized to be the underlying mechanisms of pathogenic extra-intestinal manifestations in FAP patients (Gómez and Knoers 2009; Nelson and Näthke 2013). This connection is supported by the presence of symptoms similar to Gardner syndrome in cilia-related disorders, and by the fact that APC is critical for the degradation of β-catenin in the Wnt-signaling pathway. Therefore, this pathway-specific function of APC may create a new context for therapeutic options for patients with Gardner syndrome.
We gratefully acknowledge support from the Mayo Clinic Center for Individualized Medicine, Nelson Fund, and the Mayo Clinic Department of Otorhinolaryngology, Head and Neck Surgery.