April - June 2025, Volume 21, Issue 2

Aksu OB, Gungor H, Leblebici CB, Kutlay N, Erdogan MF

From "Infantile" to Elderly: A Rare Cause of Hypercalcemia not to be Missed in the Geriatric Population

Acta Endo (Buc) 2025, 21 (2): 272-276
doi: 10.4183/aeb.2025.272

Idiopathic infantile hypercalcemia (IIH) is a rare, parathyroid hormone (PTH)–independent disorder of calcium metabolism. It is most often caused by mutations in the CYP24A1 gene that impair vitamin D catabolism. We report a 70-year-old male with persistent hypercalcemia (Ca 13.2 mg/dL) and low-normal PTH levels. Extensive evaluation excluded malignancy, granulomatous disease, and vitamin D intoxication. Genetic analysis revealed a homozygous CYP24A1 variant (c.233G>T; p.Gly78Val), consistent with CYP24A1 deficiency. Bisphosphonate therapy with zoledronic acid rapidly and sustainably normalized calcium levels for 10 months. The patient’s daughter was a heterozygous carrier. This confirmed autosomal-recessive inheritance. This case illustrates an atypical late-onset presentation of CYP24A1 deficiency. It emphasizes the importance of considering this diagnosis in adults with PTH-independent hypercalcemia, especially when seasonal variation and family history are present. Recognition of CYP24A1 deficiency at all ages highlights the need for genotype-based terminology rather than the misleading label "infantile" hypercalcemia.

Keywords: CYP24A1, Hypercalcemia, Vitamin D Metabolism.

Correspondence: Ozge Bas Aksu, MD, Ankara University Faculty of Medicine, Department of Endocrinology and Metabolism, Ibn-i Sina Hospital, Talatpasa Blv No:82, 06230 Altindag/Ankara, Turkiye, E-mail: ozgebasaksu@gmail.com