Delayed Diagnosis of HDR (Hypoparathyroidism, Deafness, and Renal Dysplasia) Syndrome Presenting With Life-Threatening Hypercalcemic Crisis: A Case Report.

Hypoparathyroidism, sensorineural deafness, and renal dysplasia (HDR) syndrome is a rare autosomal dominant disorder caused by pathogenic variants in the GATA3 gene. Because the components of the clinical triad may emerge at different stages of life, isolated evaluation of findings by different specialties may lead to delayed syndromic diagnosis. In this report, we present the case of a 39-year-old female patient who was diagnosed with hypoparathyroidism following a hypocalcemia-related tetanic convulsion at the age of five years and was found to have sensorineural hearing loss during childhood. Although chronic kidney disease developed in adulthood, the multisystemic findings were not evaluated collectively, and a syndromic diagnosis was not established. The patient presented to the emergency department with altered consciousness, dehydration, and oliguria. Evaluation revealed severe hypercalcemia (20.7 mg/dL) and acute kidney injury on the background of chronic kidney disease (creatinine: 2.98 mg/dL; estimated glomerular filtration rate: 19 mL/minute/1.73 m²). Following urgent hemodialysis and intensive intravenous hydration, serum calcium levels normalized. However, complete recovery of renal function was not achieved. Genetic analysis identified a heterozygous pathogenic GATA3 frameshift variant (c.431dup), which confirmed the diagnosis of HDR syndrome. This case emphasizes the importance of a syndromic approach and early genetic evaluation in patients presenting with hypoparathyroidism, hearing loss, and renal anomalies. In addition, careful individualization of calcium and active vitamin D replacement in individuals with reduced renal reserve appears critical to prevent life-threatening hypercalcemic complications.