Introduction: Isolated IgA deficiency (SIgAD) is the most common form of primary immunodeficiency. Patients with SIgAD have an increased risk of both systemic and organ-specific autoimmune diseases. Autoimmune thyroid diseases (AITD) and type 1 diabetes mellitus (T1DM) are the most common autoimmune endocrine disorders. They occur frequently together, and this combination is nominated as autoimmune polyglandular syndrome type 3 (APS 3). Primary hyperparathyroidism (PHPT) is the most common cause of hypercalcemia, most cases occur in women, mainly as a sporadic disease, most often caused by a single adenoma.
Case report: A 55-year-old woman with a past history of diabetes mellitus was admitted to the hospital for hypercalcemia found on routine laboratory testing. Her family history is negative for hypercalcemia or endocrine tumors. In addition to the presence of vitiligo, the patient was found to have AITD (anti-thyroid peroxidase antibody-positive subclinical hypothyroidism) and anti-glutamic acid decarboxylase antibody-positive diabetes mellitus (T1DM). Subsequent workup confirmed the presence of PHPT (elevated total 3.21 mmol/l and ionized serum calcium 1.70 mmol/l; serum creatinine level was normal; urinary calcium excretion was 7.7 mmol/24 h; serum intact PTH 393 pg/ml inappropriately elevated; bone densitometry showed T scores at the lumbar spine of −2.5, at the total hip of −1.7, and at the distal radius of −3.0; (99 m)Tc-sestamibi scintigraphy localized abnormal lower right parathyroid gland). Immunological investigation revealed SIgAD with serum IgA < 0.24 g/l in the presence of normal levels of other immunoglobulin isotypes and no history of recurrent infections. The patient was cured after parathyroidectomy, histopathological diagnosis was parathyroid adenoma.
Conclusion: There are only rare cases of immune-mediated hyperparathyroidism, associated with anti-calcium- sensing receptor autoantibodies, frequently in context with other immune diseases. The case presented here describes association of PHPT caused by adenoma with APS 3 and SIgAD. Genetic basis for this antibody deficiency and associated autoimmunity remains to be defined.
Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.
Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.