Familial hypocalciuric hypercalcaemia type 3: AP2S1 missense mutation

Area of Science:

• Endocrinology
• Medical Genetics

Background:

• Hypercalcaemia and osteoporosis management presents diagnostic challenges.
• Familial hypocalciuric hypercalcaemia (FHH) is an uncommon genetic disorder affecting calcium homeostasis.

Observation:

• A 45-year-old male presented with hypercalcaemia, low vitamin D, and osteoporosis.
• Initial diagnosis of primary hyperparathyroidism led to surgery, but hypercalcaemia persisted.

Findings:

• Genetic analysis revealed a p.arg15cys mutation in the AP2S1 gene, confirming FHH type 3.
• Low urinary calcium levels, initially attributed to vitamin D deficiency, are characteristic of FHH.

Implications:

• Accurate genetic diagnosis is crucial for managing FHH and preventing complications.
• This case highlights the importance of considering genetic causes in persistent hypercalcaemia.