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Open access

Jane J Tellam, Ghusoon Abdulrasool, and Louise C H Ciin

Summary

Distinguishing primary hyperparathyroidism (PHPT) from familial hypocalciuric hypercalcaemia (FHH) can be challenging. Currently, 24-h urinary calcium is used to differentiate between the two conditions in vitamin D replete patients, with urinary calcium creatinine clearance ratio (UCCR) <0.01 suggestive of FHH and >0.02 supportive of PHPT. A 26-year-old Caucasian gentleman presented with recurrent mild hypercalcaemia and inappropriately normal parathyroid hormone (PTH) following previous parathyroidectomy 3 years prior. He had symptoms of fatigue and light-headedness. He did not have any other symptoms of hypercalcaemia. His previous evaluation appeared to be consistent with PHPT as evidenced by hypercalcaemia with inappropriately normal PTH and UCCR of 0.0118 (borderline low using guidelines of >0.01 consistent with PHPT). He underwent parathyroidectomy and three parathyroid glands were removed. His calcium briefly normalised after surgery, but rose again to pre-surgery levels within 3 months. Subsequently, he presented to our centre and repeated investigations showed 24-h urinary calcium of 4.6 mmol/day and UCCR of 0.0081 which prompted assessment for FHH. His calcium-sensing receptor (CASR) gene was sequenced and a rare inactivating variant was detected. This variant was described once previously in the literature. His mother was also confirmed to have mild hypercalcaemia with hypocalciuria and, on further enquiry, had the same CASR variant. The CASR variant was classified as likely pathogenic and is consistent with the diagnosis of FHH. This case highlights the challenges in differentiating FHH from PHPT. Accurate diagnosis is vital to prevent unnecessary surgical intervention in the FHH population and is not always straightforward.

Learning points:

  • Distinguishing FHH from PHPT with co-existing vitamin D deficiency is difficult as this can mimic FHH. Therefore, ensure patients are vitamin D replete prior to performing 24-h urinary calcium collection.
  • Individuals with borderline UCCR could have either FHH or PHPT. Consider performing CASR gene sequencing for UCCR between 0.01 and 0.02.
  • Parathyroid imaging is not required for making the diagnosis of PHPT. It is performed when surgery is considered after confirming the diagnosis of PHPT.
Open access

Daniela Gallo, Sara Rosetti, Ilaria Marcon, Elisabetta Armiraglio, Antonina Parafioriti, Graziella Pinotti, Giuseppe Perrucchini, Bohdan Patera, Linda Gentile, Maria Laura Tanda, Luigi Bartalena, and Eliana Piantanida

Summary

Brown tumors are osteoclastic, benign lesions characterized by fibrotic stroma, intense vascularization and multinucleated giant cells. They are the terminal expression of the bone remodelling process occurring in advanced hyperparathyroidism. Nowadays, due to earlier diagnosis, primary hyperparathyroidism keeps few of the classical manifestations and brown tumors are definitely unexpected. Thus, it may happen that they are misdiagnosed as primary or metastatic bone cancer. Besides bone imaging, endocrine evaluation including measurement of serum parathyroid hormone and calcium (Ca) levels supports the pathologist to address the diagnosis. Herein, a case of multiple large brown tumors misdiagnosed as a non-treatable osteosarcoma is described, with special regards to diagnostic work-up. After selective parathyroidectomy, treatment with denosumab was initiated and a regular follow-up was established. The central role of multidisciplinary approach involving pathologist, endocrinologist and oncologist in the diagnostic and therapeutic work-up is reported. In our opinion, the discussion of this case would be functional especially for clinicians and pathologists not used to the differential diagnosis in uncommon bone disorders.

Learning points:

  • Brown tumors develop during the remodelling process of bone in advanced and long-lasting primary or secondary hyperparathyroidism.
  • Although rare, they should be considered during the challenging diagnostic work-up of giant cell lesions.
  • Coexistence of high parathyroid hormone levels and hypercalcemia in primary hyperparathyroidism is crucial for the diagnosis.
  • A detailed imaging study includes bone X-ray, bone scintiscan and total body CT; to rule out bone malignancy, evaluation of bone lesion biopsy should include immunostaining for neoplastic markers as H3G34W and Ki67 index.
  • If primary hyperparathyroidism is confirmed, selective parathyroidectomy is the first-line treatment.
  • In advanced bone disease, treatment with denosumab should be considered, ensuring a strict control of Ca levels.
Open access

S Hamidi, S Mottard, M J Berthiaume, J Doyon, M J Bégin, and L Bondaz

Summary

Brown tumors (BTs) are expansile osteolytic lesions complicating severe primary hyperparathyroidism (PHPT). Clinical, radiological and histological features of BTs share many similarities with other giant cell-containing lesions of the bone, which can make their diagnosis challenging. We report the case of a 32-year-old man in whom an aggressive osteolytic lesion of the iliac crest was initially diagnosed as a giant cell tumor by biopsy. The patient was scheduled for surgical curettage, with a course of neoadjuvant denosumab. Routine biochemical workup prior to denosumab administration incidentally revealed high serum calcium levels. The patient was diagnosed with PHPT and a parathyroid adenoma was identified. In light of these findings, histological slices of the iliac lesion were reviewed and diagnosis of a BT was confirmed. Follow-up CT-scans performed 2 and 7 months after parathyroidectomy showed regression and re-ossification of the bone lesion. The aim of this case report is to underline the importance of distinguishing BTs from other giant cell-containing lesions of the bone and to highlight the relevance of measuring serum calcium as part of the initial evaluation of osteolytic bone lesions. This can have a major impact on patients’ management and can prevent unnecessary invasive surgical interventions.

Learning points:

  • Although rare, brown tumors should always be considered in the differential diagnosis of osteolytic giant cell-containing bone lesions.
  • Among giant cell-containing lesions of the bone, the main differential diagnoses of brown tumors are giant cell tumors and aneurysmal bone cysts.
  • Clinical, radiological and histological characteristics can be non-discriminating between brown tumors and giant cell tumors. One of the best ways to distinguish these two diagnoses appears to be through biochemical workup.
  • Differentiating brown tumors from giant cell tumors and aneurysmal bone cysts is crucial in order to ensure better patient care and prevent unnecessary morbid surgical interventions.
Open access

Bidhya Timilsina, Niranjan Tachamo, Prem Raj Parajuli, and Ilan Gabriely

Summary

A 74-year-old woman presented with progressive lethargy, confusion, poor appetite and abdominal pain. She was found to have non-PTH-mediated severe hypercalcemia with renal failure and metabolic alkalosis. Extensive workup for hypercalcemia to rule out alternate etiology was unrevealing. Upon further questioning, she was taking excess calcium carbonate (Tums) for her worsening heartburn. She was diagnosed with milk-alkali syndrome (MAS). Her hypercalcemia and alkalosis recovered completely with aggressive hydration along with improvement in her renal function. High index of suspicion should be maintained and history of drug and supplements, especially calcium ingestion, should be routinely asked in patients presenting with hypercalcemia to timely diagnose MAS and prevent unnecessary tests and treatments.

Learning points:

  • Suspect milk-alkali syndrome in patients with hypercalcemia, metabolic alkalosis and renal failure, especially in context of ingestion of excess calcium-containing supplements.
  • Careful history of over-the-counter medications, supplements and diet is crucial to diagnose milk-alkali syndrome.
  • Milk-alkali syndrome may cause severe hypercalcemia in up to 25–30% of cases.