A Case of Proximal Myopathy Resulting from Multiple Causes: Parathyroidectomy was unsuccessful in presence of co-existing inclusion body myositis

We describe here a 73 year old woman who was referred to the endocrine clinic with hypercalcaemia and worsening proximal myopathy of the lower limbs. She was diagnosed with hypercalcaemia secondary to mild primary hyperparathyroidism four years previously. She was taking levothyroxine for hypothyroidism. She was referred to neurology as well. Her blood results also suggested vitamin D deficiency. She underwent muscle biopsy which was diagnostic of Inclusion body myositis. Thus she had multiple causes contributing to proximal myopathy, i.e. Inclusion body myositis, hyperparathyroidism, vitamin D deficiency and long standing hypothyroidism. She was treated with methotrexate with no improvement of her myopathy. As hypercalcaemia with excess Parathyroid hormone can worsen myositis, after repletion of vitamin D, she underwent parathyroidectomy. When she last visited the clinic her serum calcium and vitamin D were normal but there had been no improvement in her myopathy. This was owing to her co-existent Inclusion body myositis.

Keywords
Hyperparathyroidism, Hypercalcaemia, Vitamin D deficiency, Inclusion body myositis, proximal myopathy.