Hypercalcemic crisis is a set of symptoms associated with high calcium level (Ca > 3.8 mmol/L). This dangerous condition might occur in patients with primary hyperparathyroidism (PHPT).

A retrospective analysis of a high volume center was performed between 2004 and 2023 to identify cases of PHPT with Ca levels > 3.8 mmol/L. Furthermore, a case report of HC is presented.

In our cohort of 3299 surgeries for PHPT, there were 29 patients (0.88%) with preoperative Ca levels > 3.8 mmol/L. Case Report: A 56-year-old man was diagnosed with PHPT (sonography; Ca 3.2mmol/l; PTH 30.9pmol/l) and planned for elective surgery. Despite treatment with cinalcet, progression of hypercalcemia led to hospitalization (Ca 4.4mmol/l). Calcium levels decreased with conservative therapy. Scintigraphy was performed for pre-operative planning. Awaiting his surgery, patient developed a collapse condition with hematoma of the neck and mediastinum and vomiting leading to aspiration and intubation. Furthermore, dialysis and circulatory support were initiated. Acute surgical intervention was indicated: extirpation of two parathyroid glands, cervical drainage of the mediastinal hematoma, and tracheostomy. Immediate effect of surgery was observed: patient regained consciousness, circulatory support and dialysis was terminated and decannulation of tracheostomy was performed. No long-term consequences were noted during one-year follow-up.

Despite the rarity of the condition, hyperalcemic crisis might be life-threatening and should always be considered in PHPT patients with acute clinical deterioration. Prompt diagnosis and surgical treatment are essential to save the patient.