Background <p>Hypercalcemic crisis from a functioning parathyroid adenoma (PA) is exceptionally rare in prepubertal children and typically presents with a non-specific complaint such as polyuria or lethargy. We report a 7-year-old girl who was urgently referred for acute, colicky abdominal pain and repeated vomiting, which clinically mimicked acute appendicitis. During the work-up, extensive metabolic tests incidentally revealed severe hypercalcemia and elevated intact parathyroid hormone (PTH), which led to the diagnosis of PA-induced hypercalcemic crisis.Her initial manifestation was an acute abdomen rather than renal or neuropsychiatric symptoms. The case underscores that functioning PA should be included in the differential diagnosis of children presenting with unexplained gastrointestinal distress, and illustrates that timely diagnosis and focused parathyroidectomy can effectively reverse biochemical abnormalities, alleviate skeletal symptoms, and mitigate the risk of serious long-term complications.</p> Case presentation <p>We report the case of a seven-year-old female patient who was hospitalized due to complaints of abdominal discomfort accompanied by episodes of recurrent vomiting.Subsequent analysis revealed that these symptoms may represent acute gastrointestinal syndrome in the context of a hypercalcemic crisis.We describe her clinical course, diagnostic workup, and treatment. Laboratory tests revealed severe hypercalcemia (4.67 mmol/L; reference range: 2.1–2.7mmol/L), along with hypophosphatemia, hypomagnesemia, and markedly elevated PTH (268.1 pg/mL).Thyroid ultrasound revealed a nodule in the inferior aspect of the right lobe of the thyroid gland, which was subsequently confirmed by contrast-enhanced CT.After urgent management of hypercalcemia—including intravenous fluids, furosemide, salmon calcitonin, and pamidronate—the patient underwent surgical excision of the right inferior parathyroid gland.Histopathological examination confirmed the diagnosis of a benign PA. Serum calcium and PTH levels normalized within 24 hours postoperatively, with complete resolution of clinical symptoms. Marked hypocalcemia developed within several days postoperatively and was corrected. During follow-up to date, serum calcium,PTH levels, and ultrasound examination of the parathyroid have been normal.</p> Conclusions <p>PA represents an uncommon yet manageable cause of hypercalcemic crisis in pediatric patients. Timely assessment of serum calcium and PTH levels in individuals presenting with unexplained gastrointestinal symptoms—such as nausea, vomiting, or abdominal pain—facilitates swift diagnosis, thereby reducing the need for unnecessary diagnostic procedures like extensive imaging or invasive tests.Surgical resection of the PA is the first-line treatment. Postoperatively, prevention of hungry bone syndrome and long-term follow-up are required.</p>