Endocrine Abstracts

JOINT10

Introduction: Familial hypocalciuric hypercalcemia (FHH) is a genetic disorder that causes lifelong hypercalcemia, often mimicking primary hyperparathyroidism (PHPT). FHH is primarily due to calcium-sensing receptor (CASR) gene mutations, leading to altered calcium homeostasis. This report discusses a case of FHH in a 68-year-old patient, highlighting the diagnostic challenges and clinical management strategies.

Case Presentation: A 68-year-old woman, Mrs. F.A, with a medical history of hypertension, type 2 diabetes mellitus complicated by chronic kidney disease, and gout, was referred for the evaluation of hypercalcemia. Initial laboratory tests revealed a corrected serum calcium level of 119 mg/l, hypophosphatemia (27 pg/l), and elevated parathyroid hormone (PTH) levels (five times the normal range). The 24-hour urinary calcium excretion was markedly low (<20 mg/l), suggesting hypocalciuria, with a fractional excretion of calcium less than 0.01. The patient’s clinical examination showed an overweight status (BMI 28 kg/m²) but was otherwise unremarkable. Cardiovascular and respiratory examinations were normal. The absence of endocrinopathies and a lack of familial history of hypercalcemia were noted. Imaging studies, including cervical ultrasound, MIBI scintigraphy, and MRI, did not reveal parathyroid adenomas.

Discussion: FHH is often misdiagnosed as PHPT due to overlapping clinical and biochemical features. Both conditions present with hypercalcemia and non-suppressed PTH levels. However, FHH is characterized by hypocalciuria, a key differentiating factor. Genetic testing, although not performed in this case due to cost constraints, can confirm the diagnosis by identifying mutations in the CASR gene. Management of FHH typically involves conservative measures, as most patients are asymptomatic and do not require surgical intervention. In contrast, PHPT often necessitates parathyroidectomy. In this case, the patient was managed with hydration and regular monitoring of calcium levels.

Conclusions: This case underscores the importance of considering FHH in the differential diagnosis of hypercalcemia, particularly in the presence of hypocalciuria. Accurate diagnosis is crucial to avoid unnecessary surgical procedures and to implement appropriate management strategies. Further genetic studies could enhance our understanding and diagnosis of FHH, ensuring better patient outcomes.