NSD3::NUTM1 fusion evidenced on RNA sequencing in poorly differentiated thyroid cancer: a report of two cases.

SUMMARY: This case highlights a potentially underrecognised complication - acute rectal calcinosis with ulceration in the context of parathyroidectomy due to primary hyperparathyroidism (PHPT), which is a common endocrine disorder characterised by excessive secretion of parathyroid hormone (PTH), most often due to a solitary adenoma of the parathyroid gland. While severe hypercalcaemia is a known complication, its association with visceral metastatic calcifications, particularly in the rectum, is extremely rare and has not previously been reported. We describe a case of a 73-year-old female who presented with progressive symptoms of hypercalcaemia, including significant weight loss, gastrointestinal involvement, and lethargy. After repeated emergency department attendances, a hypercalcaemic crisis was confirmed. Despite initial rehydration and supportive therapy, her condition deteriorated, requiring hemofiltration. Further evaluation confirmed PHPT, revealing markedly elevated intact parathormone (iPTH) and a 5 cm parathyroid adenoma, which was removed surgically. The day following parathyroidectomy, the patient developed acute rectal bleeding with a significant haemoglobin drop. Computed tomography imaging showed rectal wall thickening and hyperdensity, while colonoscopy revealed deep rectal ulcerations with visible calcifications and inflammation. Conservative treatment, including blood component transfusions, electrolyte management, and local haemostasis, led to gradual clinical improvement.

LEARNING POINTS: Severe hypercalcaemia can lead to visceral calcifications, ischaemic changes, and gastrointestinal complications, even if not initially evident. In patients with primary hyperparathyroidism, acute rectal bleeding following parathyroidectomy may indicate a rare cause such as rectal calcinosis and should be considered in the differential diagnosis. Calcinosis should be particularly suspected in cases with a severe clinical picture of hyperparathyroidism-related hypercalcaemia (e.g. severe weight loss, lack of calcium correction after standard therapy). Early diagnosis and conservative management can result in favourable outcomes without the need for invasive treatment.