Paraganglioma (PGL) is a rare disorder (MIM 168000) characterised by tumours of the paraganglia, a collection of neuroendocrine tissues and small organs which are distributed throughout the body. The normal paraganglia play an important role in homeostasis either by acting directly as chemical sensors or by secreting catecholamines in response to stress. PGL is broadly categorised into two groups, those occurring in the head and neck region and those occurring elsewhere, with the adrenal medulla being the major site. Tumours in the head and neck have been detected in nearly 20 distinct locations including the jugular, vagal, tympanic, and aortic paraganglia, however the carotid body is the major site.¹ The paraganglia of the head and neck region have sensory innervation and function as chemoreceptors. They are associated with the parasympathetic nervous system and are located in the vicinity of major arteries and nerves. The tumours usually present as an asymptomatic slow growing mass, lacking endocrine activity. The tumours are mostly benign but local expansion can cause cranial nerve deficit, invasion of the skull base, and eventually compression of the brain stem.

The incidence of head and neck PGL is difficult to determine, however estimates range from 1 in 30 000 to 1 in 100 000 in the general population.^2,3 To date, four genetic loci have been implicated in the pathogenesis of head and neck PGL. PGL1 was mapped to the long arm of chromosome 11 at 11q23 in several Dutch^4,5 and North American families.^6–8 Candidate gene analysis in the region revealed germline mutations in the succinate dehydrogenase subunit D (SDHD) gene in families carrying the PGL1 locus.⁹ Linkage analysis of another unrelated Dutch pedigree revealed the presence of a second more proximal locus (PGL2) on 11q13.¹⁰ This locus remains unconfirmed. PGL3 …