Endocrine Abstracts

Introduction: Primary hyperparathyroidism (PHPT) is most commonly sporadic and in rare circumstances, it can develop as part of multiple endocrine neoplasia (MEN). There are few cases described in the literature reporting an association of PHPT with myasthenia gravis and multiple autoimmune syndrome (MAS). These patients may present only with clinical signs of PHPT making it difficult to suspect the coexistence of MAS. Here, we report the case of type 3 MAS in a woman with PHPT due to a parathyroid adenoma.

Observation: A 53-year-old female patient consulted our department for asthenia. She had hypothyroidism due to Hashimoto’s thyroiditis, treated with levothyroxine. She had also pernicious anemia treated with vitamin B12 replacement. Her TSH and hemoglobin levels were within the normal reference range. The diagnosis of PHPT was made after a phosphocalcic assessment showing the association of hypercalcemia at 2.89 mmol/l (2,25-2,65 mmol/l) with hypophosphatemia at 0.77 mmol/l (0,8-1,2 mmol/l) and elevated PTH level at 95 pg/ml (10-65 pg/ml). Morphological and functional exams confirmed a right inferior parathyroid adenoma. screening for MEN was negative. She underwent parathyroidectomy and kept a normal serum calcium level (2.28 mmol/l) during the follow-up. The patient was still asthenic with onset of skeletal muscle weakness leading to the diagnosis of myasthenia gravis. Her acetylcholine receptor antibodies levels were positive (1.2 mmol/l; reference range: <0.5 nmol/l).

Discussion: The coexistence of myasthenia gravis with autoimmune thyroid disease and pernicious anemia is well-recognized as type 3 MAS. PHPT is known to be associated with MEN and only few cases reports mentioned its presence with myasthenia gravis and thymoma. Screening for thymoma is necessary since it is present in 15% of myasthenia gravis cases and since thymus and parathyroid glands have common embryologic origin.