Increased urinary dopamine excretion in association with bilateral carotid body tumours: clinical, biochemical and genetic findings

This report describes a rare case of a patient with increased urinary dopamine excretion in association with bilateral carotid body tumours. Excretion of adrenaline, noradrenaline, metadrenaline, normetadrenaline and 4-hydroxy-3-methoxymandelic acid (HMMA) were within the reference ranges, and an 123I-meta-iodobenzylguanidine (MIBG) scan showed uptake in the neck masses, with no other abnormal uptake anywhere else in the body. The patient is being managed conservatively as the tumours are not amenable to resection on account of their size and vascularity. There are only four previous case reports of dopamine-secreting tumours of the carotid body described in the literature, all of whom were women. The tumours were unilateral in three cases and bilateral in the fourth case. Familial cases of carotid body tumours have a higher prevalence of bilateral tumours than non-familial cases. Recent reports in the literature have suggested that a significant number of patients with extra-adrenal catecholamine-secreting paragangliomas have a genetic mutation in one of the identified susceptibility genes for catecholamine-secreting tumours, despite having no other affected family members, and a mutation has been found in the succinate dehydrogenase gene for this patient.