SDHB gene positive metastatic paraganglioma associated with lesions which demonstrate both positive and negative uptake of 18FDG PET and 131MIBG

### Learning Points for Clinicians Paragangliomas are rare caetacholamine secreting neuroendocrine tumours. The diagnosis and management of these tumours is often difficult, particularly as a diagnosis of metastases is often made retrospectively when disease recurrence occurs. In recent years, the role of genotyping has allowed us to better predict which tumours are more likely to be metastatic. Mutations in the SDHB gene have been associated with higher rates of metastatic disease.1 Unfortunately, mutations in this gene can also lower the sensitivity of radiolabeled metaiodobenzylguanidine (MIBG). MIBG scanning is considered the gold standard imaging modality for the diagnosis of recurrent disease but this case illustrates the potential diagnostic pitfalls associated with this imaging modality in cases of SDHB gene mutations. The case demonstrates the importance of genotyping as a diagnostic and predictive tool and the importance of clinical acumen in the face of negative test results. This gentleman underwent a MRI of pelvis in February 2011 for investigation of possible sacroiliitis on a background of known inflammatory bowel disease. This MRI demonstrated a 2.3 × 2.3 cm nodule posterior to the pubic …