This Article Full Text Full Text (PDF) Submit a related Letter to the Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Google Scholar Articles by Lietman, S. A. Articles by Levine, M. A. PubMed PubMed Citation Articles by Lietman, S. A. Articles by Levine, M. A. Related Collections Pediatric Endocrinology Calcium and Bone Metabolism

A Novel Loss-of-Function Mutation, Gln459Arg, of the Calcium-Sensing Receptor Gene Associated with Apparent Autosomal Recessive Inheritance of Familial Hypocalciuric Hypercalcemia

Departments of Orthopaedic Surgery (S.A.L.) and Biomedical Engineering (S.A.L., C.D., M.A.L.), Cleveland Clinic Lerner Research Institute and Foundation, Cleveland, Ohio 44195; Pediatric Endocrine Unit (Y.T.-R.), Ha’ Emek Medical Center, Afula and Technion Faculty of Medicine, Haifa 31096, Israel; Section of Biochemistry (T.S.J., W.Y.-C.), Department of Pathology and Laboratory Medicine, Taipei Veterans General Hospital Taipei, Taiwan, Republic of China 112; Department of Medical Research and Education (Y.D.-M.), Taipei Veterans General Hospital and Institute of Biophotonics, National Yang-Ming University, Taipei 112, Taiwan; Clalit Health Service (N.K.), Aom El Ganem, Tel Aviv 62098, Israel; and Division of Endocrinology and Diabetes (M.A.L.), The Children’s Hospital of Philadelphia and Department of Pediatrics (M.A.L.), University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104

Address all correspondence and requests for reprints to: Dr. Steven A. Lietman, Department of Orthopaedic Surgery/A41, The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, Ohio 44195. E-mail: lietmas{at}ccf.org.

Context: Mutations that inactivate one allele of the gene encoding the calcium sensing receptor (CaSR) cause autosomal dominant familial hypocalciuric hypercalcemia (FHH), whereas homozygous mutations cause neonatal severe hyperparathyroidism.

Objective: We describe the identification and biochemical characterization of a novel CASR gene mutation that caused apparent autosomal recessive FHH in an extended consanguineous kindred.

Design: The study design involved direct sequence analysis of the CaSR gene, clinical and biochemical analyses of patients, and in vitro immunobiochemical studies of the mutant CaSR.

Results: A novel inactivating mutation (Q459R) was identified in exon 4 of both alleles of the CASR in the proband, who presented with asymptomatic hypercalcemia and hypocalciuria at age 2 yr. The proband’s parents were heterozygous for the Q459R mutation consistent with autosomal recessive inheritance of FHH. Among 13 family members that were studied, eight subjects were heterozygous for the Q459R mutation and five had normal genotypes. All heterozygous subjects were asymptomatic and normocalcemic apart from one subject who was mildly hypercalcemic. The Q459R mutant CaSR was normally expressed at the cell membrane but retained only 30–50% of the calcium-dependent activity of the wild-type CaSR.

Conclusion: We identified a novel loss-of-function Q459R mutation in the CASR gene that exhibits mildly reduced sensitivity to calcium and that is associated with apparent autosomal recessive transmission of FHH. This study demonstrates the importance of genetic testing in FHH to distinguish between de novo and inherited mutations of the CASR gene and assist in management decisions.