Shaker, Joseph

Abstract Calcitriol-induced hypercalcemia is most frequently caused by granulomatous and inflammatory conditions such as sarcoidosis as well as lymphoma. Recently, pathogenic CYP24A1 variants resulting in inability of the 24-hydroxylase enzyme to deactivate 1,25(OH)2D has been found to be a cause of calcitriol-induced hypercalciuria and hypercalcemia in children and adults. Patients may present with hypercalcemia, suppressed PTH, hypercalciuria, and renal stones. We describe 4 young women and 1 man with calcitriol-associated hypercalcemia in whom pathogenic CYP24A1 variants were found to be the cause. In 2 of the 3 women who became pregnant, hypercalcemia worsened (the calcium was not checked during pregnancy in the third). Lactation was associated with worsened hypercalcemia in the 2 women who breast-fed. In the other woman who did not become pregnant, serum calcium levels varied from high normal to markedly elevated often without an explanation. The male patient was a middle-aged man with a long history of kidney stones and hypercalcemia as well as a family history of kidney stones. Gene sequencing confirmed that each patient had 2 variants in CYP24A1. We share 5 cases of a rare condition and further broaden the presentation of CYP24A1 variants to not only include worsening hypercalcemia in pregnancy, but also during lactation. Further calcium levels may vary markedly in patients with this condition. Physicians should consider pathogenic CYP24A1 variants in patients with unexplained calcitriol-associated hypercalcemia/hypercalciuria.

Abstract Disclosure: M. Sokrab: None. V.S. Rao: None. P. Shah: None. J.L. Shaker: None. A 47 year-old woman was evaluated 2/2024 for bone pain especially in the forearms and lower legs. The symptoms were worse since about 4/2023. Initial evaluation 11/2023 revealed elevated alkaline phosphatase levels and markers of bone remodeling (P1NP 396 ug/dl, normal; 20-101 and C-telopeptide 4389, normal; 177-1015. The plasma fluoride level was 17.1 mcmol/L (normal; < 4.1). There was no history of excess exposure to fluoride from dental products. She did not drink powdered iced tea or use green tea capsules. There was no industrial fluoride exposure and she consumed city water. She used inhaled fluticasone twice weekly but was not taking other fluoride containing medications, particularly voriconazole. She reported huffing computer cleaner containing difluoroethane between mid 2023 and early 2024. On examination, she had diffuse skeletal tenderness especially over her forearms and lower legs. Lab data revealed calcium 9.2 mg/dl (normal, 8.6-10.2), albumin 4 g/dl, phosphorus 3.6 mg/dl (normal, 2.5-4.5), creatinine 1.08 mg/dl (normal, 0.5-1.1), ionized calcium 1.33 mmol/l (normal, 1.18-1.33), pH normalized ionized calcium 1.25 mmol/l (normal, 1.18-1.33), PTH 126 pg/ml (normal, 15-72), 25(OH)vitamin D 29.5 ng/ml (normal, 20-50), and alkaline phosphatase 287 u/l (normal, 40-120) with a predominant elevation of the bone isoenzyme. The bone specific alkaline phosphatase was 93.4 mcg/l (normal, 7.0-22.4). The SPEP revealed a biclonal IgG Kappa monoclonal protein too small to quantify. The repeat fluoride level was 1.2 mg/l (normal, <0.05). Imaging included diffuse uptake on bone scan as well as periostitis/periosteal thickening involving legs, arms, and hands. There was axial osteosclerosis. Our patient appears to have skeletal fluorosis. Although the time-line of reported huffing and symptoms is not completely consistent, we could find no other exposure to fluoride and speculate she may have been huffing before she recalls. Skeletal fluorosis (SF) is endemic in some countries generally related to drinking water or tea that is high in fluoride, In the US, SF is caused by abnormal use of fluoride-containing dental products, excessive consumption of powdered iced tea containing fluoride, chronic use of the antifungal agent voriconazole and now more often huffing abuse of computer cleaners containing difluoroethane. The number of reported cases of huffing-related SF appears to be increasing and greater awareness of this problem is needed. Presentation: 6/1/2024

Abstract Primary hyperparathyroidism (PHPT) is classically characterized by hypercalcemia with elevated or inappropriately normal parathyroid hormone (PTH) levels. Elevated PTH levels in the presence of normal calcium levels are not infrequently found during the evaluation of metabolic bone disorders or kidney stone disease. This can be caused by secondary hyperparathyroidism (SHPT) or normocalcemic primary hyperparathyroidism (NPHPT). NPHPT is due to autonomous parathyroid function whereas SHPT is caused by a physiologic stimulation to PTH secretion. Many medical conditions and medications can contribute to SHPT, and differentiation between SHPT and NPHPT may be difficult. Cases are presented to illustrate examples. In this paper, we review the distinction between SHPT and NPHPT as well as end organ effects of NPHPT and outcomes of surgery in NPHPT. We suggest that the diagnosis of NPHPT be made only after careful exclusion of causes of SHPT and consideration of medications that can increase PTH secretion. Further, we advise a conservative approach to surgery in NPHPT.

Abstract Mutations in one of the two genes encoding type I procollagen (COL1A1 and COL1A2) are frequently the cause of osteogenesis imperfecta (OI), a disorder characterized by brittle bones. Here we tested whether patients with low bone density also have mutations in these genes. The 26 patients studied had no apparent metabolic bone disease, but most had a positive family history of osteopenia or osteoporosis. Although a diagnosis of OI was considered by the clinician in some cases, the clinical criteria for OI were not satisfied. Our strategy for mutation analysis consisted of PCR amplification of cDNA made to fibroblast mRNA using primers specific for the coding regions of COL1A1 and COL1A2. The PCR products were then sequenced directly with primers located within each PCR product. We found that 3 of 26 patients had mutations that altered the encoded amino acid. One mutation, at position α2(I)-661 has been reported (Spotila et al. 1991 Proc Natl Acad Sci USA PNAS 88: 5423). The other 2 patients, who were not related to each other, had a mutation that altered the proline codon at α1(I)-27 to alanine. This mutation was not found in 81 normal individuals or in 37 additional osteopenic individuals. However, its effect on the biologic function of type I collagen, as well as its role in osteopenia, is uncertain. In addition to the two mutations, we found a polymorphism in codon α2(I)-459. Although this polymorphism involved an amino acid substitution, it was present with equal frequency in the patient and the normal population. By analyzing this and previously reported neutral sequence variants in the COL1A2 gene, we determined that all patients expressed both alleles of the COL1A2 gene. The 12 patients who were heterozygous for a COL1A1 neutral sequence variant also expressed both alleles. Here we present all PCR primer and sequencing primer information. The results suggest that surveying a larger group of similarly selected individuals may reveal additional mutations in the COL1A1 or COL1A2 genes.