Succinate dehydrogenase mutations
SDHB mutation carriers may develop benign or malignant phaeochromocytomas and paragangliomas, renal, gastrointestinal stromal and possibly thyroid tumours. SDHD is associated with phaeochromocytomas and paragangliomas. SDHC carriers often present with a single benign tumour only. The diagnosis requires genetic testing in all cases.
General examination
To diagnose succinate dehydrogenase mutations a detailed and full general examination is mandatory in the initial assessment of all endocrine patients.
Blood pressure
Blood pressure will typically be elevated, but may revert to normal between attacks.
Skin and mucous membranes
Neurofibromata, 'cafe au lait' patches, axillary freckling and neuromas would suggest alternative causes of familial phaeochromocytoma.
Abdomen
Gentle examination of the abdomen should be performed for possible masses. Deep palpation is inappropriate as this may trigger an attack in patients with functioning tumours.
Lymph nodes
The risk of malignant disease is greatly increased with SDHB mutations.
Thyroid
Medullary cell carcinoma is associated with phaeochromocytoma in multiple endocrine neoplasia type 2.
Pituitary status
Examine pituitary status in all patients as pituitary tumours have been described in association with phaeochromocytomas in SDHB. Clinical examination and baseline assessment of pituitary function is therefore appropriate, though routine imaging is unnecessary.
Neurological system
Full neurological examination is necessary due to the association of phaeochromocytomas with haemangioblastomas in VHL, which can occur through out the central nervous system.
Urine microscopy
Urine should be analysed in all patients with phaeochromocytoma seeking evidence of end organ damage due to hypertension and as a screen for renal tumours.