Endocrine Abstracts

Case history: We present the case of a 72-year-old female who was referred to the endocrinology service following the identification of a pathogenic germline mutation in the SDHA gene (c.91C>T, p.Arg32*) as part of a genetic panel for hypertrophic cardiomyopathy. There was no personal or family history of phaeochromocytoma or paraganglioma (PPGL), gastrointestinal stromal tumours or pituitary adenoma.

Investigations: Our patient was reviewed in our specialist SDH clinic and underwent surveillance screening including assessment of metanephrine levels and non-contrast MR imaging (skull base to pelvis). She reported no symptoms of catecholamine excess and was normotensive (BP 134/62 mmHg, HR 78 bpm) on 150 mg Irbesartan. 24 hour urinary metanephrines were within the reference range: normetadrenaline 1681 nmol/24h (<4400 nmol/24h), metadrenaline 795 nmol/24h (<2000 nmol/24h) and 3-methoxytyramine 950 nmol/24h (<2500 nmol/24h). Non-contrast MRI revealed a 3 × 3.6 cm lesion at the left carotid bifurcation, consistent with a carotid body paraganglioma. No other SDH-related lesions were identified on imaging.

Results and treatment: Due to the patients’ comorbidities of cardiomyopathy and primary hyperparathyroidism and the identified lesion being non-secretory, a decision was made for active surveillance. She underwent an interval MRI at six months follow-up which revealed an unchanged appearance of the paraganglioma. She will undergo a further surveillance MRI at a one-year interval from the preceding scan. In the interim, she is undergoing assessment and optimisation by the cardiology team.

Conclusions and points for discussion: It is now widely accepted that patients who carry SDH mutations should undergo surveillance screening. The aim of surveillance programmes is for early identification of tumours, recurrence, and metastases to allow timely intervention. As genetic testing is becoming more accessible, cascade genetic testing is leading to the identification of increasing numbers of asymptomatic familial carriers. These asymptomatic individuals should be entered into surveillance screening programmes to allow early detection of PPGLs and other associated lesions. The modality and frequency of this surveillance however is still controversial. SDHA mutations are less common than SDHB and SDHD mutations and therefore there are fewer reported cases and a limited understanding of the best surveillance for these individuals. To our knowledge, we report the first case of a surveillance screen detected PPGL to be found in an asymptomatic individual with previously identified SDHA mutation status. Previous literature has debated the need for surveillance screening in SDHA carriers due to estimated low penetrance rates. This case highlights the importance of at least an initial surveillance screening in all newly identified SDHA mutation carriers.