Case Presentation: Functional Assessment of a CASR Variant Identified in a Patient with Hypercalcaemia Confirms Familial Hypocalciuric Hypercalcaemia in the Patient and a Sister Previously Misdiagnosed with Primary Hyperparathyroidism

Table 1

Patients’ biochemical data.

Patient	Date of reading	Serum ionized calcium (pH 7.4) (mmol/L)	Plasma total calcium (corrected) (mmol/L)	Urine calcium excretion (µmol/L GF)	Calcium/creatinine clearance ratio	Serum intact PTH (pmol/L)
A	November 2019	1.43^a	2.63^b	8^e	0.0029	9.2^h
	November 2021	1.40^a	2.74^b	15^f	0.0056	7.5^h
B	April 2009 (6 months pre-PTX)	1.39^a	2.52^c	22^g	0.0086	5.3^i
	September 2009 (immediately post-PTX)	nd	2.44^c	nd	nd	2.5^j
	December 2009 (2.5 months post-PTX)	nd	2.52^c	nd	nd	4.2^i
	May 2010 (8 months post-PTX)	nd	2.54^c	nd	nd	3.4^i
	November 2022 (∼13 years post-PTX)	1.38^a	2.40^d	nd	nd	6.5^h

Parathyroidectomy (PTX) performed on 29^th September, 2009; serum ionized calcium reference range: ^a1.12–1.32 mmol/L; plasma total calcium (corrected) reference ranges: ^b2.20–2.60 mmol/L, ^c2.15–2.55 mmol/L, and ^d2.10–2.60 mmol/L; urine calcium excretion reference ranges: ^e33–112 µmol/L GF, ^f47–166 µmol/L GF, and ^g24–84 µmol/L GF; serum intact PTH reference ranges: ^h1.6–9.0 pmol/L, ⁱ0.7–7.0 pmol/L, and ^j1.3–6.8 pmol/L; nd = not determined.