Hereditary gingival fibromatosis (HGF) and amelogenesis imperfecta (AI) are two rare oral conditions with genetic etiologies. The case of a 17-year-old boy affected by HGF, AI, anterior open bite, and pyramidal impaction of the maxillary molars is reported. Internal bevel gingivectomies were carried out to reduce gingival overgrowth. Clinical examination of the family revealed the presence of HGF and AI in his 12-year-old sister (both in milder forms) and of HGF in his older half brother. Genetic sequencing analyses were performed to detect any of the known mutations leading to HGF and AI. Histologic analysis revealed the presence of fibroepithelial hyperplasia, consistent with a diagnosis of GF. Sequencing genetic analysis failed to identify any of the common mutations leading to HGF (SOS-1) or AI (enamelin and amelogenin genes). This phenotype, similar to what has been described in other families, may represent a new syndrome caused by an as-yet unknown genotype. Schlagwörter: amelogenesis, fibromatosis, genetic, gingival, mutation, syndrome