Beyond Routine Workup: Renal Calcifications and Cysts Prompt Genetic Testing

Introduction: Although chronic kidney disease (CKD) is often attributed to common causes such as diabetes, some patients present with atypical features that require deeper investigation. Diagnostic clues may lie in subtle imaging findings or elements of medical history that suggest an alternative diagnosis. In this case, an unusual combination of renal and endocrine findings led to genetic testing and a diagnosis with broader clinical implications. Case Description: 57M with progressive CKD and a history of recurrent nephrolithiasis was evaluated. Current creatinine was 2.6 mg/dL (eGFR 28 mL/min/1.73 m2). Past medical history included parathyroid carcinoma treated with parathyroidectomy and radiation, resulting in hypoparathyroidism managed with calcitriol and calcium. Exam was unremarkable. Urine sediment was benign. Renal ultrasound revealed bilateral simple cysts and medullary nephrocalcinosis. Kidney biopsy showed advanced medullary fibrosis, moderate vascular sclerosis, and focal dystrophic calcification, with no monoclonal deposits. Given the combination of renal and endocrine findings, genetic testing was performed, revealing a pathogenic mutation in the CDC73 gene. Discussion: This case highlights how atypical renal imaging findings, such as medullary nephrocalcinosis and renal cysts, combined with a history of parathyroid carcinoma, can signal an underlying genetic disorder. The identification of a CDC73 mutation confirmed the diagnosis of hyperparathyroidism-jaw tumor (HPT-JT) syndrome, a rare inherited condition which causes parathyroid carcinoma, ossifying jaw tumors and uterine and testicular neoplasms. Renal manifestations include cysts, nephrocalcinosis, hamartomas, and Wilms tumor. Guidelines support genetic testing in adults with CKD of unclear etiology, particularly when accompanied by structural abnormalities, extrarenal features, or a relevant family history. Targeted next-generation sequencing panels are cost-effective and high-yield. Genetic confirmation allows for diagnostic clarity, appropriate cancer surveillance, and family counseling, including the possibility of preimplantation genetic testing. This case emphasizes the critical role of nephrologists in recognizing diseases with multi-organ involvement.