Adult Summary Report

Secondary Findings in Adult Subjects

Non-diagnostic, excludes newborn screening & prenatal testing/screening

• Status (Adult): Passed (Consensus scoring is Complete)
• Curation Status (Adult): Released 1.1.1
• GENE/GENE PANEL: MAX, SDHA, SDHAF2, SDHB, SDHC, SDHD, TMEM127
• Condition: Paragangliomas 1, 2, 3, 4, 5; Pheochromocytoma
• Mode(s) of Inheritance: Autosomal Dominant

Actionability Assertion

• MAX ⇔ 171300 (pheochromocytoma): Assertion Pending
• SDHA ⇔ 614165 (paragangliomas 5; pgl5): Assertion Pending
• SDHAF2 ⇔ 601650 (paragangliomas 2; pgl2): Assertion Pending
• SDHB ⇔ 115310 (paragangliomas 4; pgl4): Assertion Pending
• SDHC ⇔ 605373 (paragangliomas 3; pgl3): Assertion Pending
• SDHD ⇔ 168000 (paragangliomas 1; pgl1): Assertion Pending
• TMEM127 ⇔ 171300 (pheochromocytoma): Assertion Pending

Actionability Rationale

This topic was initially scored prior to development of the process for making actionability assertions. The Actionability Working Group decided to defer making an assertion until after the topic could be reviewed through the update process.

Final Consensus Scores

Gene Condition Pairs: MAX ⇔ (OMIM:171300) SDHA ⇔ (OMIM:614165) SDHAF2 ⇔ (OMIM:601650) SDHB ⇔ (OMIM:115310) SDHC ⇔ (OMIM:605373) SDHD ⇔ (OMIM:168000) TMEM127 ⇔ (OMIM:171300)

Outcome / Intervention Pair	Severity	Likelihood	Effectiveness	Nature of the Intervention	Total Score
Paraganglioma development / Surveillance	2	3C	3B	3	11CB

1. What is the nature of the threat to health for an individual carrying a deleterious allele?

Prevalence of the Genetic Condition

Hereditary paraganglioma-pheochromocytoma (PGL/PCC) syndrome represents 30% of all PGL/PCC. The prevalence is approximately 1:500,000 for PCC and 1:1,000,000 for PGL. [1]

Clinical Features

Hereditary PGL/PCC syndromes are characterized by PGLs that arise from neuroendocrine tissue (paraganglia) distributed from the skull base to the pelvic floor and PCCs, PGLs that are confined to the adrenal medulla. PGLs in the skull base and neck (e.g., carotid body, vagal, and jugulotympanic) are associated with the parasympathetic nervous system and do not secrete catecholamines. PGLs in the thorax, abdomen, and pelvis are typically associated with the sympathetic nervous system and may hypersecrete catecholamines. Gastrointestinal stromal tumors (GISTs) may also occur in individuals with a pathogenic variant in SDHD, SDHA, SDHC, or SDHB. Renal clear cell carcinoma (RCC) and papillary thyroid carcinoma have been reported with pathogenic variants in SDHB and SDHD. Symptoms of PGL/PCC result from mass effects (e.g., hearing loss, tinnitus, cough, hoarseness, or difficulty swallowing for head and neck tumors) or catecholamine hypersecretion from sympathetic PGLs and PCCs (e.g., elevations in blood pressure and pulse, headache, episodic profuse sweating, forceful palpitations, pallor, and apprehension or anxiety). The risk for malignant transformation is greater for extra-adrenal sympathetic PGLs than for PCCs or skull base and neck PGLs. [1, 2, 3, 4, 5]

Natural History

Compared to individuals with sporadic tumors, individuals with SDHD, SDHAF2, SDHC, and SDHB pathogenic variants tend to present at younger ages, are more likely to have multifocal, bilateral, and recurrent disease, and have multiple synchronous neoplasms. SDHD is associated with parasympathetic skull base and neck PGLs, with ~50% presenting as multiple tumors and a <5% malignancy risk. SDHAF2 is associated with PGLs of the skull base and neck, with ~90% presenting as multiple tumors and a low malignancy risk. SDHA is associated with PGLs generally presenting as single tumors with a low malignancy risk. SDHC is associated with parasympathetic skull base and neck paragangliomas, with ~20% presenting as multiple tumors and a low malignancy risk. SDHB is associated with extra-adrenal sympathetic PGLs, with ~20% presenting as multiple tumors and a 34-97% malignancy risk, and, less frequently, benign or malignant PCCs and parasympathetic PGLs. SDHB is associated with higher morbidity and mortality compared to other genes, may develop malignant disease at any paraganglion site, and may predict a shorter survival for malignant PCCs and PGLs. MAX is associated with PCCs, with ~60% presenting as bilateral tumors and a 25% malignancy risk. A subset of individuals with MAX pathogenic variants may also go on to develop PGLs, but typically present with PCC initially. TMEM127 is associated with PCCs, with ~40% presenting as bilateral tumors and a <5% malignancy risk.
Age of onset of has been reported as 14-47 years for SDHD, 29-47 years for SDHB, 28-35 for MAX, and 34-72 for TMEM127. Age at onset for SDHA, SDHAF2, and SDHC is unclear. PGL/PCCs may be fatal, but with targeted treatment based on tumor stage, some affected individuals have lived for 20 years or more. For PGL/PCCs that have not metastasized, operative treatment can be curative. However, once metastases have occurred, the disease is uniformly fatal, with only 50% of affected individuals surviving beyond 5 years. No reliable pathology studies are available to distinguish a primary benign from a primary malignant PGL/PCC. [1, 2, 3, 4, 5, 6, 7, 8, 9]

2. How effective are interventions for preventing harm?

Patient Management

At diagnosis, the following are recommended to establish the extent of disease:
• Imaging studies using MRI/CT, 123-1-MIBG, and possibly PET to identify tumors
• Consider evaluation for GISTs in young adults who have unexplained gastrointestinal symptoms (e.g., abdominal pain, upper gastrointestinal bleeding, nausea, vomiting, difficulty swallowing) or who experience unexplained intestinal obstruction or anemia
• Consider screening for RCC in individuals with SDHB pathogenic variants
• Medical genetics consultation. (Tier 4) [2]

Surveillance

Regular clinical monitoring by a physician or medical team with expertise in treatment of hereditary PGL/PCC syndromes. (Tier 4) [2]

Lifelong biochemical and clinical surveillance beginning at age 10 years or ≥10 years before the earliest age of diagnosis in the family is recommended. The type and timing of the surveillance should be based on which gene is affected and take into account known genotype-phenotype relationships, with special attention for patients with pathogenic variants in SDHB due to the high risk of malignant disease. (Tier 2) [10, 11]

The following gene-specific monitoring has been proposed based on penetrance data suggesting that if lifelong screening were to begin at age 10, disease would be detected in all persons with a pathogenic variant in SDHD and 96% of persons with a pathogenic variant in SDHB:
• Individuals should undergo 24-hour urinary excretion of fractionated metanephrines and catecholamines with follow-up imaging as needed
• For SDHD or SDHC, periodic (e.g., every 2 years) MRI or CT of the skull base and neck to detect PGLs and periodic (e.g., every 4 years) body MRI or CT and 123-I-MIBG scintigraphy to detect PGLs or metastatic disease that may occur beyond the neck and skull base
•For SDHB, periodic (e.g., every 2 years) MRI or CT of the abdomen, thorax, and pelvis to detect PGLs and periodic (e.g., every 4 years) 123-I-MIBG scintigraphy to detect PGLs or metastatic disease that may not be detected with MRI or CT. (Tier 4) [2, 4]

Early detection of tumors through surveillance and removal of tumors may prevent or minimize complications related to mass effects, catecholamine hypersecretion, and malignant transformation or metastasis. In addition, factors associated with longer survival seems to be an early diagnosis and excision of the primary tumor, and, whenever possible, aggressive excision of any recurrence or soft-tissue metastases. Surgical resection is the mainstay for treatment for both benign and malignant PGL/PCCs. (Tier 2) [4, 11]

Though there is no available evidence specific to HPPS-related surveillance and surgery, a meta-analysis of 7 studies (N= 2,634) indicated that risk of recurrent disease after complete resection was 2.24 events/100 person-years (95% CI: 1.62, 2.87) for studies that include a majority of patients with genetic or syndromic disease (e.g., von Hippel Lindau). (Tier 1) [12]

Circumstances to Avoid

Penetrance of hereditary PGL/PCC syndromes may be increased in those who live in high altitudes or are chronically exposed to hypoxic conditions. Avoidance of habitation at high altitudes and activities that promote long-term exposure to hypoxia should be considered. In one study, individuals with SDHD pathogenic variants diagnosed with single tumors at their first clinical evaluation lived at lower average altitudes and were exposed to lower altitude-years than those with multiple tumors (p<0.012). (Tier 3) [2]

Activities, such as cigarette smoking, that predispose to chronic lung disease should be discouraged in individuals who have a pathogenic variant in SDHD, SDHA, SDHAF2, SDHC, SDHB, or MAX. (Tier 4) [2]

3. What is the chance that this threat will materialize?

Mode of Inheritance

Autosomal Dominant

Prevalence of Genetic Variants

Among hereditary PGL/PCC, approximately 30% of cases are attributed to pathogenic variants in SDHD, 4-8% are attributed to SDHC, 22-38% are attributed to SDHB, and 0.6-3% with SDHA. The proportions attributed to SDHAF2, MAX, and TMEM127 are unclear. (Tier 3) [2]

Penetrance

Though data is limited, pathogenic variants in SDHD, SDHAF2, SDHA, SDHC, and SDHB appear to have a high but age-related penetrance. (Tier 3) [2]

For SDHD, penetrance of any outcome is 48% by age 30 and 86% by age 50. The penetrance of skull base and neck PGLs is 68% by age 40, while the penetrance of extra-adrenal abdominal or thoracic tumors is 35% by age 60. For SDHB, penetrance of any outcome is 29% by age 30, <50-77% by age 50, and 100% by age 80. The penetrance of skull base and neck PGLs by age 40 is 15%, while the penetrance of extra-adrenal abdominal or thoracic tumors by age 60 is 69%. (Tier 3) [2]

The pooled risk based on prevalence studies malignant PGL for SDHD and SDHB is estimated to be 4% (95% CI: 2-7%) and 13% (95% CI: 4-34%), respectively. (Tier 1) [5]

In a large Dutch family, out of 45 individuals with a variant in SDHAF2, 33 with paternal inheritance of the variant developed the disease, 5 (median age 42 years) with paternal inheritance of the variant had not developed overt PGL, and 7 (median age 74 years) with maternal inheritance of the variant were unaffected. (Tier 3) [13]

A summary of 62 individuals with SDHC pathogenic variants noted that 77% had developed at least one tumor, though all were index cases. A study focused on 8 index cases indicated that none of the first-degree relatives had developed tumors, suggesting lower penetrance for all carriers. (Tier 5) [14]

A prospective study of 11 individuals with MAX pathogenic variants (8 index patients and 3 relatives), 37 individuals with SDHA pathogenic variants (29 index patients and 8 relatives), and 29 individuals with TMEM127 pathogenic variants (20 index patients and 9 relatives) estimated penetrance by age 40 years as 73% (95% CI: 28-90%) for MAX, 39% (95% CI: 21-53%) for SDHA, and 41% (95% CI: 20-57%) for TMEM127. The penetrance in relatives with an SDHA variant was significantly lower compared with index patients by age 40 (13% versus 45%, p<0.001). However, a difference in penetrance between index patients compared with relatives was not identified for MAX (50% vs 22%, p=0.26) or TMEM127 (88% vs 33%, p=0.69], but these results have to be interpreted with caution owing to the low case numbers in these subgroups. (Tier 5) [15]

Relative Risk

Information on relative risk was not available for the Adult context.

Expressivity

Variation in the prevalence, penetrance, and phenotypic expression of pathogenic variants of the SDH subunits (SDHD, SDHA, SDHC, SDHB) may be population specific. In addition, phenotypes vary among individuals and even among family members with the same pathogenic variant. (Tier 3) [2]

The age-dependent penetrance and variable expressivity of SDHA, SDHD, SDHAF2, SDHC, SDHD, and MAX pathogenic variants, as well as the parent-of-origin effects associated with SDHD, SDHAF2, and MAX pathogenic variants, predict that a substantial number of individuals who have inherited these variants will be simplex cases. (Tier 4) [2]

An individual who inherits an SDHD, SDHAF2, or MAX pathogenic variant from his/her mother is at low but not negligible risk of developing disease, though exceptions do occur. An individual who inherits an SDHD, SDHAF2, or MAX pathogenic variant from his/her father is at high risk of manifesting PGL and PCC. (Tier 4) [2]

4. What is the Nature of the Intervention?

Nature of Intervention

Interventions include regular biochemical monitoring with subsequent imaging as indicated (MRI or CT and 123-I-MIBG scintigraphy).

5. Would the underlying risk or condition escape detection prior to harm in the setting of recommended care?

Chance to Escape Clinical Detection

PCCs and extra-adrenal sympathetic PGLs in hereditary PGL/PCC syndromes present in a manner similar to those in persons with sporadic tumors, most often coming to medical attention due to the signs and symptoms associated with catecholamine hypersecretion or signs and symptoms related to mass effects from the neoplasm. Diagnosis may be delayed due to the rarity of the tumors, absence of symptoms due to inactivated catecholamine, and non-specificity of signs and symptoms. The average time lag from the onset of hypertension to the diagnosis of the tumor is 3 years, with the tumors often diagnosed incidentally. Regular screening is recommended beginning at diagnosis, or earlier for family members. These screenings are above and beyond general population recommendations. [2, 4]

Date of Search: 03.10.2015 (updated 10.31.2017)

Reference List

1. Hereditary pheochromocytoma-paraganglioma. Orphanet encyclopedia, http://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=en&Expert=29072

2. S Kirmani, WF Young. Hereditary Paraganglioma-Pheochromocytoma Syndromes. 2008 May 21 [Updated 2014 Nov 06]. In: RA Pagon, MP Adam, HH Ardinger, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2024. Available from: http://www.ncbi.nlm.nih.gov/books/NBK1548

3. Online Medelian Inheritance in Man, OMIM®. Johns Hopkins University, Baltimore, MD. PARAGANGLIOMAS 1; PGL1. MIM: 168000: 2016 Aug 23. World Wide Web URL: http://omim.org.

4. Plouin PF, Gimenez-Roqueplo AP. Pheochromocytomas and secreting paragangliomas. Orphanet J Rare Dis. (2006) 1:49.

5. van Hulsteijn LT, Dekkers OM, Hes FJ, Smit JW, Corssmit EP. Risk of malignant paraganglioma in SDHB-mutation and SDHD-mutation carriers: a systematic review and meta-analysis. J Med Genet. (2012) 49(12):768-76.

6. Online Medelian Inheritance in Man, OMIM®. Johns Hopkins University, Baltimore, MD. PARAGANGLIOMAS 4; PGL4. MIM: 115310: 2016 Oct 06. World Wide Web URL: http://omim.org.

7. Online Medelian Inheritance in Man, OMIM®. Johns Hopkins University, Baltimore, MD. PHEOCHROMOCYTOMA. MIM: 171300: 2016 Jul 26. World Wide Web URL: http://omim.org.

8. Online Medelian Inheritance in Man, OMIM®. Johns Hopkins University, Baltimore, MD. MAX PROTEIN; MAX. MIM: 154950: 2016 Aug 18. World Wide Web URL: http://omim.org.

9. Online Medelian Inheritance in Man, OMIM®. Johns Hopkins University, Baltimore, MD. TRANSMEMBRANE PROTEIN 127; TMEM127. MIM: 613403: 2013 Sep 06. World Wide Web URL: http://omim.org.

10. National Comprehensive Cancer Network. Neuroendocrine Tumors. (2017) Website: www.nccn.org

11. Lenders JW, Duh QY, Eisenhofer G, Gimenez-Roqueplo AP, Grebe SK, Murad MH, Naruse M, Pacak K, Young WF Jr. Pheochromocytoma and paraganglioma: an endocrine society clinical practice guideline. J Clin Endocrinol Metab. (2014) 99(6):1915-42.

12. Amar L, Lussey-Lepoutre C, Lenders JW, Djadi-Prat J, Plouin PF, Steichen O. MANAGEMENT OF ENDOCRINE DISEASE: Recurrence or new tumors after complete resection of pheochromocytomas and paragangliomas: a systematic review and meta-analysis. Eur J Endocrinol. (2016) 175(4):R135-45.

13. Online Medelian Inheritance in Man, OMIM®. Johns Hopkins University, Baltimore, MD. PARAGANGLIOMAS 2; PGL2. MIM: 601650: 2016 Sep 19. World Wide Web URL: http://omim.org.

14. Else T, Marvin ML, Everett JN, Gruber SB, Arts HA, Stoffel EM, Auchus RJ, Raymond VM. The clinical phenotype of SDHC-associated hereditary paraganglioma syndrome (PGL3). J Clin Endocrinol Metab. (2014) 99(8):E1482-6.

15. Bausch B, Schiavi F, Ni Y, Welander J, Patocs A, Ngeow J, Wellner U, Malinoc A, Taschin E, Barbon G, Lanza V, Soderkvist P, Stenman A, Larsson C, Svahn F, Chen JL, Marquard J, Fraenkel M, Walter MA, Peczkowska M, Prejbisz A, Jarzab B, Hasse-Lazar K, Petersenn S, Moeller LC, Meyer A, Reisch N, Trupka A, Brase C, Galiano M, Preuss SF, Kwok P, Lendvai N, Berisha G, Makay O, Boedeker CC, Weryha G, Racz K, Januszewicz A, Walz MK, Gimm O, Opocher G, Eng C, Neumann HPH. Clinical Characterization of the Pheochromocytoma and Paraganglioma Susceptibility Genes SDHA, TMEM127, MAX, and SDHAF2 for Gene-Informed Prevention. JAMA Oncol. (2017) 3(9):1204-1212.