Endocrine Abstracts

Case History: A 19-year-old female presented with painful left shoulder after slipping whilst doing press-ups. Plain x-ray showed a proximal humeral fracture, as well as a large bone cyst raising concerns of a pathological fracture. She had no past medical history and was not taking any regular medications. On further questioning she did complain of a 2 year history of bilateral painful shoulders and left knee pain. Family history was significant for her father suffering primary hyperparathyroidism aged 27 which resolved spontaneously. Paternal grandmother had recently been diagnosed with primary hyperparathyroidism (aged > 50). She was referred to the local fracture clinic, and due to the x-ray appearances she was also referred to the sarcoma service.

Investigations: MRI of both shoulders suggested bilateral proximal humeral metaphyseal aneurysmal bone cysts (ABC). Subsequent whole body MRI showed cystic lesions in both proximal humeri, as well as within the left ilium, right fibula and left distal femur. Fluoroscopic guided biopsy of the left distal femur lesion showed giant cell-rich tumour of bone, with no evidence of malignancy.

Results and treatment: Biochemistry showed parathyroid hormone 82.8 pmol/l (1.6-6.9), corrected calcium 3.33 mmol/l (2.2-2.6), phosphate 0.61 mmol/l (0.8-1.5), Vitamin D 41.7 nmol/l (>50). On review there was a previously unreported lesion in her right lower parathyroid gland on the whole body MRI, and MIBI SPECT scan confirmed increased tracer uptake in this area, in keeping with a right inferior parathyroid adenoma. A diagnosis of pHPT was made and cinacalcet was commenced. The patient underwent an urgent right lower parathyroidectomy and histopathology confirmed parathyroid adenoma. Calcium normalised without complication. Genetic testing revealed heterozygous deletion of exons 4-7 in CDC 73 gene, confirming the diagnosis of HPT-JT.

Conclusion and points for discussion: Hyperparathyroidism jaw tumour syndrome (HPT-JT) is a rare autosomal dominant inherited endocrine neoplasia syndrome that predisposes to parathyroid adenomas and carcinomas, ossifying fibromas of the jaw, and renal and uterine tumours.¹ HPT-JT is associated with deletions in the CDC73 tumour suppressor gene.² Despite its appearance in the name, ossifying jaw tumours are only present in 50% of cases of HPT-JT.² Patients require lifelong surveillance due to risk of parathyroid carcinoma and extra-parathyroid tumours. This case highlights the importance of considering family history and wider genetic testing in young patients with primary hyperparathyroidism. Cascade testing allows for early detection and treatment to reduce risk of complications.