Endocrine Abstracts

JOINT757

Hyperparathyroidism-Jaw Tumor Syndrome (HPT-JP) is a rare autosomal dominant syndrome with incomplete penetrance characterized by the combination of primary hyperparathyroidism (PHPT), renal lesions, jaw tumors and benign and malignant uterine lesions. Atypical parathyroid tumor and carcinoma are overrepresented in HPT-JT than in sporadic or other forms of familiar PHPT. The syndrome is caused by the germline mutation of CDC73 encoding parafibromin. A 13-years old adolescent was referred to our outpatient clinic shortly after the surgical resection of the left inferior parathyroid gland which was diagnosed as atypical parathyroid tumor. The clinical history begun 2 months earlier with severe symptomatic PHPT (total serum calcium 16,6 mg/dl and PTH: 221 pg/mL). Neck ultrasound revealed a 1-cm lesion consistent with the left inferior parathyroid gland. This lesion was also detected by ^18F-Fluorocholina PET-CT but not by planar TC-sestamibi parathyroid scintigraphy. The family history was significant for PHPT affecting the patient’s mother, three maternal first cousins and one maternal second cousin. Given the histology, the young age and the family history, genetic testing was performed, revealing a heterozygous germline deletion of all exons of the CDC73 gene. This confirmed the diagnosis of HPT-JT. The patient’s mother and one maternal first cousin carried the same deletion. Following this result, imaging of the jaw and kidney was performed, but no abnormalities were detected. After surgery, the patient developed hungry bone syndrome, which was managed with calcium carbonate and calcitriol. These treatments were gradually tapered over five months until they were discontinued. The patient has undergone regular biochemical and instrumental evaluation and remains in remission 16 months after surgery (total serum calcium level 10 mg/dl and PTH 17,20 ng/l). In conclusion, in young patient with PHPT, it is mandatory to thoroughly explore the family history and perform genetic testing to ensure an accurate diagnosis and to guide the appropriate follow up.