Endocrine Abstracts

Familial hypocalciuric hypercalcaemia (FHH) is a benign condition, occurs as a result of inactivating mutation in the calcium sensing receptor (CASR) gene and is autosomal dominant.

We present a 56-year-old lady with periodic mild hypercalcaemia since 2004. Her highest corrected calcium concentration was 2.76 mmol/l (NR 2.2–2.6). She was asymptomatic. Her parathyroid hormone concentration was also mildly elevated at 9.7 pmol/l (NR 1.6–6.9). Her urinary calcium output was 3.96 mmol (NR 2.5–7.5).

She had parathyroidectomy for suspected primary hyperparathyroidism (PHPT) in 2008 (two glands removed – no adenoma on histology). She was on vitamin D supplements and her last vitamin D level was normal at 71 nmol/l (NR >49.9 nmol/l). She was referred to our hospital in April 2013 for persistent mild hypercalcaemia. She remained asymptomatic.

Her 23-year-old son has also been diagnosed with PHPT at a different hospital and he was listed for parathyroidectomy as well. He too had mild hypercalcaemia with the highest value of 2.72 mmol/l and highest corrected value of 2.64 mmol/l. His PTH level was 5.2 pmol/l and his urinary calcium output was very low at 0.21 mmol.

We suspected the diagnosis of FHH in view of their mild biochemical derangements, low urinary calcium and family history. We contacted the other hospital and asked them to perform genetic testing which later confirmed that the mother and the son were heterozygous for c.61G>A (p.Gly21Arg) CASR variant. This gene has been reported in the literature to be associated with FHH.

This case illustrates the importance of making the correct diagnosis of FHH by genetic testing in order not to label these younger patients as hyperparathyroid and wrongly referring them for surgery. We have shown here that we saved a young person from having a surgical operation unnecessarily and without any proven benefits.