Background: Familial hypocalciuric hypercalcaemia (FHH) is a rare condition due to inactivating mutations in the calcium-sensing receptor gene (CASR). Usually, patients have mild hypercalcaemia with no or minimal complications.
Case: A 27-year-old male had a history of recurrent pancreatitis. Each admission was associated with significantly elevated corrected calcium up to 3.4 mmol/L with an inappropriately normal PTH. Calcium creatinine clearance of 0.00135 was suggestive of FHH. He continued to have recurrent pancreatitis with elevated calcium out of proportion to what is expected with FHH so consideration of dual pathology with primary hyperparathyroidism was considered. Sestamibi parathyroid imaging demonstrated a parathyroid adenoma posterior to the right inferior thyroid lobe with a correlating lesion also seen on 4D CT. He proceeded with surgical resection of the right inferior parathyroid, histopathology was consistent with hyperplasia. Despite this, he continued to have significantly elevated calcium and episodes of pancreatitis. Genetic testing was performed and identified a variant of uncertain significant affecting the CASR gene. Ongoing hypocalciuria and the genetic test result was thought to be supportive of a diagnosis of FHH. He was commenced on cinacalcet which led to a drastic reduction in hospital admissions, on occasions where he had run out of tablets, he represented to hospital within 1 week with abdominal pain and elevated corrected calcium to 3.3 mmol/L. With titration of cinacalcet to 60mg BD, calcium improved to 2.7 mmol/L and there had been no further hospital presentations.
Discussion: There are rare case reports of pancreatitis in FHH associated with variant mutations in the CASR.1 Cinacalcet is a calcimimetic and has previously been used for patients with FHH causing complications.2 Our patient responded very well to cinacalcet. Best long-term management of these patients is unclear, but some case series reveal sustained improvement over at least 3 years.3