It is only relatively recently that four types of hereditary paraganglioma syndromes have been identified caused by gene changes in the succinate dehydrogenase (SDH) enzyme.
These mutations are inherited in an autosomal dominant fashion so that a person with the mutation has a 1 in 2 or 50% chance of passing the mutation on to each child.
SDHD and SDHAF2:
Whilst these gene changes are inherited in the autosomal dominant manner, individuals will only develop paragangliomas if the change is inherited from their father. They can inherit the mutation from their mother, but will not develop paragangliomas. They can still pass it to their children.
Therefore, if a man inherits a gene change from his mother, he will not develop paragangliomas, but if he passes that gene change to his child, that child may develop growths. Individuals with changes in these genes have about a 70% chance of developing growths if inherited from their father. These growths are typically in the head and neck region.
Although these tumours usually do not produce hormones, large tumours may cause symptoms such as coughing, hearing loss in one ear, or difficulty swallowing.
SDHC and SDHB:
These gene changes can be inherited from either parent.
SDHC patients typically develop paragangliomas in the head or neck region that do not usually produce hormones, although large tumours may cause symptoms such as coughing, hearing loss in one ear, or difficulty swallowing. About 70% of people with the gene change may develop growths.
SDHB patients frequently develop extra-adrenal paragangliomas in the abdomen and thorax and have a higher risk of their tumours being cancerous and spreading (metastasizing). Like phaeos, these tumours may secrete hormones called catecholamines that may cause symptoms such as high blood pressure, rapid heartbeat, headaches or sweating. Less commonly these patients may also develop paragangliomas in the head and neck region, as well as kidney and thyroid cancer (papillary thyroid cancer). Only about 40-60% of people with the gene change will develop paragangliomas/phaeochromocytomas.
In addition, all patients with SDH gene changes are at risk of developing adrenal gland phaeochromocytomas.
Screening for patients with a known SDH gene change or those at 50% risk of inheriting the mutation will undergo similar screening to phaeo patients, including 24 urine collections (or plasma metadrenalines and normetadrenalines) from around the age of 5 years, annual abdominal ultrasound or MRI scans from around 7 years and neck/thorax/abdominal MRI every 3 years from age 15. The first treatment of choice is usually surgery.
Further information on phaeos and parangangliomas can be found here.
For further detailed information on Phaeochromocytomas and Paragangliomas (including MEN and SDH) please read the AMEND patient information booklet which was produced in March 2012 in collaboration with the NET Patient Foundation:
Phaeochromotyomas and Paragangliomas (1.41 MB). We recommend that you discuss the content of this booklet with your specialist - it is not for use in self-diagnosis, and not all of the information it contains may be relevant to you.
Author: Jo Grey, AMEND CEO, with the help of the AMEND Medical Advisory Team