Familial Hypocalciuric Hypercalcemia (FHH) is a rare benign condition inherited in an autosomal dominant pattern with high penetrance. This rare genetic condition is detected in approximately 2% of cases examined as primary hyperparathyroidism (PH). The Calcium Sensing Receptor (CaSR) gene's inactivating mutations result in a calcium-parathormone level-saturation curve shift to the right. Generally, the calcium level does not exceed 11,5 mg/dl and the PTH is seen normal. In our case and in her family, extreme high blood calcium levels up to 14 mg/dl and accompanying advanced parathyroid hormone levels rising up to five times the upper limit of normal were detected. Due to these high PTH levels and advanced hypercalcemia, she was thought to have PH as a primary diagnosis. The case and her family are an interesting phenomenon that do not clinically fit classical FHH.