DOI: https://doi.org/10.36347/sasjm.2026.v12i05.037

Pages: 578-580

The concurrent manifestation of Primary Hyperparathyroidism (PHPT) and Familial Hypocalciuric Hypercalcemia (FHH) within a single individual represents a diagnostic paradox. FHH is typically an autosomal dominant, benign operational shift in the homeostatic set-point of calcium, driven by inactivating germline mutations of the calcium-sensing receptor (CaSR) gene, requiring conservative management. Conversely, PHPT is a common acquired disorder of autonomous parathyroid hormone (PTH) hypersecretion requiring targeted surgical exploration to avoid renal and skeletal decompensation. This comprehensive article reviews the specific clinical case of a 56-year-old female patient presenting with severe hypercalcemia (110.5 mg/L) and elevated PTH (240 pg/mL) accompanied by persistent, verified hypocalciuria (75 mg/24h) and a localized 12x9 mm lower left parathyroid adenoma. We dissect the deep molecular cross-talk, tracking how chronic baseline parathyroid tissue stimulation in FHH may facilitate somatic clonal expansion, leading to superimposed PHPT adenomas. Furthermore, we analyse why traditional screening parameters like the fractional excretion of calcium fail during dual-pathology overlap, concluding with clinical guidelines to prevent redundant, harmful cervical explorations.