Endocrine Abstracts

JOINT143

Introduction: Primary hyperparathyroidism (PPH) and monoclonal gammopathy (MGUS) are two causes of hypercalcaemia. The association of the two is rare. Nevertheless, it has been reported in the literature, although the link has not yet been identified.

Case report: This is a 57-year-old patient who had been treated in internal medicine for MGUS for 6 months and had moderate hypercalcaemia. She presented to the emergency department with asthenia and worsening of her hypercalcaemia. A work-up showed confirmed HPP with hypophosphataemia, hyperpathormonemia and high 24-hour calciuria. A cervical ultrasound identified a parathyroid adenoma confirmed by MIBI scintigraphy.

Discussion: The association of MGUS or Multiple Myeloma (MM) and HPP is rare and may lead to diagnostic uncertainty as to the contribution of each aetiology to hypercalcaemia. In our patient, MGUS was diagnosed 6 months before HPP. One study showed that the prevalence of MGUS was 10% in patients presenting with HP. A recently published series of 5 cases (2020) reports 4 cases were diagnosed simultaneously for MM and HPP. The main hypothesis cited in the literature for this association is the induction of myeloma by high levels of PTH, which induces antiapoptotic effects on plasma cells.

Conclusion: The coexistence of two aetiologies of hypercalcaemia, MGUS and HHP, should encourage simultaneous diagnosis.

References: Arnulf et al, Arch Intern Med.2002; C.F-Blanco et al, La Revue de méd.int 28 (2007); Qamar et al ECE2020