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Hereditary paraganglioma-pheochromocytomas (PGL/PCC) are rare neuroendocrine tumors represented by paragangliomas (occurring in any paraganglia from the skull base to the pelvic floor) and pheochromocytomas (adrenal medullary paragangliomas; see this term).
Hereditary PGL/PCCs represent 30% of all PGL/PCC, for which prevalence is around 1/500,000 for PCC and 1/1,000,000 for PGL.
PGL can be either hypersecreting (catecholamines) or non-secreting and PCCs usually secrete catecholamines. Secreting (sympathetic) PGLs are predominantly found in the thoracic, abdominal and pelvic areas. Hypersecretion manifests as sustained or paroxysmal elevations in blood pressure, headache, episodic profuse sweating, palpitations, pallor and apprehension or anxiety. Urinary bladder PGL may be revealed by painless hematuria and blood pressure increase after micturition. Non-secreting (parasympathetic) PGLs are predominantly located in the head and neck and present as enlarging masses that may be asymptomatic or may be associated with unilateral hearing loss, pulsatile tinnitus, cough, hoarseness of voice, pharyngeal fullness, swallowing difficulty, pain and/or problems with tongue motion. There are no validated markers of malignancy (rate around 15%); the only criterion is the presence of metastases. Gastric stromal tumors and renal cancers are rarely associated.
Up to 10% of genetically determined PCC/PGLs are due to a SDHx germline mutation. Hereditary PCC/PGLs are caused by mutations in the SDHD, SDHC, SDHB, SDHA and SDHAF2 (or SDH5) genes (11q23, 1q21, 1p36.1-p35, 5p15 and 11q31.1 respectively). Transmission is autosomal dominant but associated with maternal genomic imprinting for SDHD and SDHAF2 and expressed when the mutation is inherited from the father. Penetrance depends on the gene, age and tumor sites. Tumors in patients with SDHB mutations are more likely to become malignant than those in patients with other SDHx mutations.
Diagnosis is based on clinical examination and family history. Young age at onset, presence of bilateral, extra-adrenal or multiple tumors, or malignancy suggest an inherited disorder. Imaging studies (MRI, CT) are used to detect tumors and may include functional imaging (scintigraphy, PET). Biochemical testing includes plasma free metanephrines and/or 24 hour-urinary fractionated metanephrines. Molecular genetic testing confirms the diagnosis.
Differential diagnoses include non-hereditary PCC/PGL (although hereditary PCC/PGL tends to present at younger ages, to be multi-focal, bilateral, and recurrent, or to have multiple synchronous neoplasms), PCC/PGL associated with other hereditary conditions (neurofibromatosis type 1, von Hippel-Lindau syndrome, multiple endocrine neoplasia type 2, Carney triad and Carney-Stratakis syndrome; see these terms) and familial PCC due to TMEM127 mutation.
Prenatal testing is not recommended. Presymptomatic testing is proposed in at-risk children from 6 years of age.
Management and treatment
Treatment for secreting tumors involves blood pressure control with alpha-blockers followed by surgery by specialized teams. If the tumors have not metastasized, surgical resection can be curative. Follow-up is required due to the risk of recurrence and malignancy in particular for SDHB mutation-carriers. For head and neck PGL, external radiotherapy can be proposed. When metastases have occurred, other treatment options including chemotherapy and targeted radiotherapy should be proposed.
The disease may be fatal, but some have lived with malignant PCC/PGL for 20 years or more.
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