Familial Hypocalciuric Hypercalcemia (FHH): This diagnosis is likely due to the patient's low calcium clearance rate, inappropriately normal PTH level, and the absence of nephrocalcinosis. The patient's long-standing hypercalcemia, as evidenced by a previous calcium level from 2019, also supports this diagnosis. FHH is a benign condition characterized by hypercalcemia, hypocalciuria, and normal or elevated PTH levels.

Primary Hyperparathyroidism: Although the low calcium clearance rate makes this diagnosis less likely, it cannot be entirely ruled out without further evaluation, such as parathyroid gland imaging or a parathyroid hormone-related peptide (PTHrP) level.
Vitamin D-mediated Hypercalcemia: Despite normal vitamin D levels, it is possible that the patient has an abnormality in vitamin D metabolism or sensitivity, contributing to hypercalcemia.

Hyperparathyroidism-Jaw Tumor Syndrome: This rare condition is characterized by hyperparathyroidism, jaw tumors, and renal lesions. It is essential to consider this diagnosis due to the potential for malignant transformation and the need for early intervention.
Malignancy-associated Hypercalcemia: Although the patient's age and presentation make this less likely, it is crucial to rule out underlying malignancies, such as lymphoma or leukemia, which can cause hypercalcemia.

Pseudohypoparathyroidism: This condition is characterized by resistance to PTH, leading to hypocalcemia, hyperphosphatemia, and elevated PTH levels. However, some variants can present with hypercalcemia, making it a rare consideration in this case.
Williams Syndrome: This genetic disorder can cause hypercalcemia, short stature, and distinctive facial features. Although rare, it is essential to consider this diagnosis in patients with unexplained hypercalcemia and developmental abnormalities.