Primary hyperthyroidism due to a parathyroid adenoma with subsequent myasthenia gravis.

Sir, There are two cases in the world literature reporting an association between myasthenia gravis with thymoma and hyperparathyroidism. In the first, the hyperparathyroidism was due to a parathyroid adenoma, 1 while in the second it was due to nodular hyperplasia. 2 Subsequently, a case with no myasthenia gravis but with a thymoma and hyperparathyroidism due to a parathyroid adenoma has been published. 3 We report a case of myasthenia gravis and hyperparathyroidism due to a parathyroid adenoma with no thymoma detected. We also raise the possibility that the myasthenia gravis was precipitated by the use of intravenous pamidronate. A 67-year-old lady, previously treated for thyrotoxicosis with radioiodine, presented to the urologists with renal colic. Laboratory investigation revealed hypercalcaemia (3.13 mmolul; normal range 2±2.6 mmolul) and a high PTH level (320 ngul; normal range 12±72 ngul). At this time, the patient reported no other symptoms. TSH was within the laboratory reference range with the patient taking thyroxine 100 mcg daily. Initial treatment of the hypercalcaemia was given with intravenous pamidronate (60 mg in 250 ml 0.9% normal saline over 4 h). Serum calcium fell from 3.13 mmolul to 2.56 mmolul over the next week. However, the patient reported that an influenza-like illness occurred on the day following the infusion, which is a recognized side-effect of pamidronate. This was followed by`difficulty using legs' and`difficulty taking the top off toothpaste and jars.' Subsequently, a speech problem was reported, with the voice becoming`higher in pitch' with inability`to get the words outÐas though choking in throat.' A strange sensation in the tongue whilst talking was also described. When the patient attended for preoperative assessment prior to parathyroidectomy, dysarthria was noted. Surgery followed with a parathyroid adenoma being successfully removed. Whilst some facial tingling was noted post-operatively, no hypocalcaemia was evident, with 1-alphacalcidol being given perioperatively, although rebound hypercalcaemia (3.53 mmolul) had occurred prior to surgery. During routine post-operative follow-up, reports of occasional double vision and difficulty swallowing were made. A diagnosis of myasthenia gravis was made, with high levels of acetylcholine receptor antibodies being detected ()10 nmolul; normal range 0±0.5 nmolul). A tensilon test was also positive, with fatigability of speech being used to assess response since no proximal muscle fatigability or reproducible ocular muscle plasies were present. Our patient was initially treated with pyrido-stigmine 30 mg qds with good response, although a relapse of her myasthenia gravis followed. Her pyridostigmine was increased to …