Familial paragliomas: The emerging impact of molecular genetics on evaluation and management

Hypothesis: Advancements in molecular genetics has direct impact on the evaluation and management of patients and family members with familial paragangliomas (FP). Background: Familial paragangliomas, in contrast to sporadic cases, are commonly multiple, bilateral, and present at an earlier age. Familial tumors are inherited in an autosomal dominant pattern with genomic imprinting of the paternal allele. Mapping studies have identified regions on chromosome llq as harboring the genetic defect responsible for paraganglioma formation. Methods: A multigenerational family with five affected females with head and neck paragangliomas underwent clinical and genetic evaluation. Genetic mapping was performed with microsatellite markers from chromosome Ilql3 and q23. Nonaffected individuals were screened for carrying the affected haplotype. In addition, by using DNA obtained from an amniotic fluid sample, in utero screening of a fetus was performed. Results: The most common complaints were hearing loss and neck masses that usually manifested by age 25. Genetic mapping identified loci 1 Iql3 and q23 as sites likely responsible for tumorogenesis. Three unaffected family members, including a fetus, were identified as carriers of the affected haplotype. The genetic findings were used to design a screening protocol for family members at risk for developing glomus tumors. Conclusions: Genetic screening of unaffected family members can identify individuals harboring the mutated allele. Identification of family members at risk for developing FP by molecular genetic techniques may lead to early detection of head and neck paragangliomas and may directly impact morbidity from glomus tumors and their treatment.