SUN-773 Hypocalcemia: A Key Clue to 22q11.2 Deletion in a 47-Year-Old

Abstract Disclosure: L. Sieh: None. M.E. Pollevick: None. A. Wilson: None. R. Mahoney: None. Background: 22q11.2 deletion syndrome is typically diagnosed prenatally or in childhood after associated findings are detected. We report a case of an adult woman with congestive heart failure but no apparent cardiac congenital abnormalities who was found to have 22q11.2 deletion. Clinical Case: A 47-year-old woman with a 4-year history of congestive heart failure was admitted for acute decompensated heart failure. A thorough physical exam revealed a flattened philtrum, dental enamel hypoplasia, a protruding tongue, and short distal phalanges in her hands. Electrocardiography noted QTc of 455. Initial testing revealed hypocalcemia (total 6.3 mmol/L, n: 8.8 - 10.3 mmol/L; ionized 0.77 mmol/L, n: 1.12 - 1.32 mmol/L) with hyperphosphatemia (6.2 mmol/L, n: 2.5 - 4.5). PTH was inappropriately normal (54.8 pg/mL, n: 15.1 - 85.7 pg/mL). Echocardiography showed left ventricular enlargement and biatrial enlargement with severely reduced EF, but no evidence of congenital cardiac defects. Lymphocyte subsets revealed a low T cell count (420 cells/uL, n<699 cells/uL) with normal CD4/CD8 ratio. She disclosed an intellectual disability, having been unable to progress past elementary school education. Previous imaging studies noted renal agenesis, an aberrant right subclavian artery, and chronic paranasal sinus disease. Given early-onset heart failure with hypoparathyroidism, T-cell lymphopenia, and intellectual disability, genetic testing was pursued. An SNP oligonucleotide microarray test revealed a 2.9 Mb microdeletion on 22q11.2. The patient was acutely treated for volume overload with diuresis with concurrent intravenous calcium repletion. Upon discharge, she was referred to outpatient endocrinology to manage hypoparathyroidism and followed up with a multidisciplinary outpatient clinic for further management of 22q11.2 deletion syndrome. Conclusions: While multiple nonspecific findings consistent with 22q11.2 deletion were present, the syndrome did not declare itself with severe illness via cardiac decompensation until the 5th decade of life. Hypoparathyroidism, suggested by profound hypocalcemia with normal PTH, was a vital clue leading to her diagnosis. 22q11.2 deletion affects 1 in 2000 births but presents heterogeneously, which can lead to diagnostic delay even to adulthood. A clinical suspicion must be maintained for 22q11.2 deletion in adults who present with related manifestations including unexplained hypoparathyroidism. Reference: (1) McDonald-McGinn, D., Sullivan, K. Chromosome 22q11.2 deletion syndrome (DiGeorge syndrome/velocardiofacial syndrome). Medicine (Baltimore) 2011;90:1-18. (2) Blagojevic, C. et al. Estimate of the contemporary live-birth prevalence of recurrent 22q11.2 deletions: a cross-sectional analysis from population-based newborn screening. CMAJ Open 2021;9:E802-809. Presentation: Sunday, July 13, 2025