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Endocrine Abstracts (2019) 63 P119 | DOI: 10.1530/endoabs.63.P119

1Department of Clinical and Experimental Medicine, Endocrine Unit, University of Pisa, Pisa, Italy; 2Department of Biomedical & Molecular Sciences, Queen’s University, Kingston, Canada.

Context: Mutations of cytochrome P450 24 subfamily A member 1 (CYP24A1) gene are associated with Idiopathic Infantile Hypercalcemia (IIH), a disease recently related to vitamin D catabolism impairment.

Aim of the study: Report of clinical and biochemical features of a large family with a novel mutation of CYP24A1.

Methods: We performed dosage of total calcium, ionized calcium, 24 h urinary calcium, PTH, 25-OH-Vitamin D (25-OH-D), and 24–25 Vitamin D, genetic analysis of CYP24A1 and abdomen ultrasound in the proband, a 44 year old man, and in first-degree relatives (Mother, Father, Sister and Two sons). Vitamin D metabolites were analyzed using liquid chromatography mass spectrometry at Queen’s University Laboratory (Kingston, Canada).

Results: The proband showed high levels of total calcium, 25-OH-D, 1,25-(OH)2-D and low levels of PTH, 24,25-(OH)2D3 and 1,24,25-(OH)3D3. 25-OH-D/24-25-OH-D ratio was high (500.5). Abdomen ultrasound showed bilateral nefrolitiasis. Genetic analysis revealed a novel homozygous mutation. In first-degree relatives, serum calcium and 25-OH-vitamin D were in the upper limit of normal range and PTH low. The 25-OH-D/24-25-OH-D ratio was normal. Abdomen ultrasound showed nefrolitiasis only in the sister. Genetic analysis confirmed the mutation in heterozygosity in each member.

Family membersCYP24A1 Mutation*Ca2+ (mmol/L)*PTH (ng/L)25-OH-D (ng/mL)24,25-(OH)2D3 (ng/mL)*25D3/24,25D31,24,25-(OH)3D3 (pg/mL)1,25-(OH)2D3 (pg/mL)Nephro-lithiasis
Proband (M 44 yr)c.667 A>T p.Arg223 Homozygous1.34671.890.14500.5<268.2yes
Sister (54 yr)c.667 A>T p.Arg223 Eterozygous1.261432.261.5420.619.756.6yes
Son (13 yr)c.667 A>T p.Arg223 Eterozygous1.331237.551.8320.415.697.2no
Son 2 (11 yr)c.667 A>T p.Arg223 Eterozygous1.372040.591.5326.31070.4no
Father (85 yr)c.667 A>T p.Arg223 Eterozygousn.a.n.a38.951.1533.610.841.6no
Mother (82 yr)c.667 A>T p.Arg223 Eterozygousn.a.n.a48.932.3720.517.238.3no
n.a.: not available*Ca2+: normal range 1,12–1,32 mmol/L * PTH: normal range 8-40 ng/L *25D3/24,25D3: normal range < 30.

Conclusions: We report the biochemical and clinical features of a family with a novel CYP24 A1 mutation. Preliminary data suggest that the new mutation is associated with a mild phenotype. However, genetic and environmental factors could contribute in the clinical outcome.

Volume 63

21st European Congress of Endocrinology

Lyon, France
18 May 2019 - 21 May 2019

European Society of Endocrinology 

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