Incomplete penetrance of a novel SDHD variation causing familial head and neck paraganglioma

Research progress on the pathogenesis of the SDHB mutation and related diseases

With the improvement of genetic testing technology in diseases in recent years, researchers have a more detailed and clear understanding of the source of cancers. Succinate dehydrogenase B (SDHB), a mitochondrial gene, is related to the metabolic activities of cells and tissues throughout the body. The mutations of SDHB have been found in pheochromocytoma, paraganglioma and other cancers, and is proved to affect the occurrence and progress of those cancers due to the important structural functions. The importance of SDHB is attracting more and more attention of researchers, however, reviews on the structure and function of SDHB, as well as on the mechanism of its carcinogenesis is inadequate. This paper reviews the relationship between SDHB mutations and related cancers, discusses the molecular mechanism of SDHB mutations that may lead to tumor formation, analyzes the mutation spectrum, structural domains, and penetrance of SDHB and sorts out some of the previously discovered diseases. For the patients with SDHB mutation, it is recommended that people in SDHB mutation families undergo regular genetic testing or SDHB immunohistochemistry (IHC). The purpose of this paper is hopefully to provide some reference and help for follow-up researches on SDHB.

Reduced Risk of Corporal Tumors in Patients With Head and Neck Paragangliomas With p.Pro81Leu Mutations

OBJECTIVE

Patients with head and neck paragangliomas who are positive for the SDHD p.Pro81Leu (P81L) mutation are thought to have a distinct phenotype from other SDHx mutations, but few studies have focused on this mutation. The objective of this study was to determine the hazard of developing a second primary, metastatic, or recurrent paraganglioma in SDHx patients with or without P81L.

STUDY DESIGN

Retrospective chart review of 60 patients with head and neck paragangliomas and genetic testing, followed for a median of 9 years.

SETTING

Single academic medical center.

METHODS

Univariable Cox proportional hazards regression evaluated second primary and recurrent paragangliomas in patients with SDHD P81L, SDHx non-P81L, and nonhereditary paraganglioma.

RESULTS

This series comprised 31 patients without SDHx, 14 with SDHD P81L, and 15 with other SDHx mutations. At a median 9 years of follow-up, corporal (not head and neck) second primary paragangliomas occurred in 31% of patients with SDHx non-P81L mutations, compared with 0% and 4% of patients with SDHD P81L and without SDHx mutations, respectively. Second corporal paragangliomas were more likely in patients with SDHx non-P81L mutations than in those without a mutation (hazard ratio = 5.461, 95% confidence interval: 0.596-50.030, p = .13).

CONCLUSION

This is the first study to report a lower likelihood of corporal tumors for patients with head and neck paragangliomas with SDH mutations positive for P81L. Larger studies are needed to determine if head and neck paraganglioma patients with P81L qualify for less intensive imaging surveillance to screen for second primary paragangliomas outside the head and neck.

A need to tailor surveillance based on family history: describing a highly penetrant familial paraganglioma kindred with an SDHD pathogenic variant

Pathogenic variants (PVs) in the SDHD gene increase risk for paragangliomas (PGL)/pheochromocytomas, renal cell carcinomas, and gastrointestinal stromal tumors. Penetrance in individuals with SDHD PVs varies in reported research from 40-70%, and there is limited evidence of specific genotype risks. This study aims to characterize a multi-generational family with SDHD p.Trp43* PVs and potential genotype-phenotype considerations for surveillance. Individuals with a paternally inherited SDHD p.Trp43*(c.129G > A) PV were identified. Genetic, medical and family histories were abstracted, including clinical characteristics, tumor histories, and treatment approaches. Eleven individuals with the SDHD PV in the same kindred were diagnosed with 41 SDHx-related tumors across all family members. Eight individuals developed 27 head and neck PGL of varying origins, and seven individuals developed tumors outside of the head and neck region. Many individuals had multiple tumors, and age of first tumor diagnosis ranged from age 10 to age 45 years old. Individuals with SDHD p.Trp43* variants may have higher risks for SDHx related tumors than other SDHD variants. Prioritizing identification of at-risk individuals and initiating surveillance tailored to family history is recommended given the rate of multiple tumors found in one familial branch of individuals under 18 years old. Individuals with strong family histories of PGL at young ages with this PV will benefit from tailored surveillance recommendations.