Carbamazepine and Myasthenia Gravis

Sir,

The letter by Kurian and King [[1]] was of particular interest to me, since one of our patients also developed myasthenia gravis while she was being treated with carbamazepine. This girl, now 16 years old, was born with a cleft palate, which was repaired at 1œ years. At the age of seven she developed epilepsy with partial and generalized seizures, and she was put on carbamazepine which had a reasonably good effect. The last seizure was at 9œ years, and carbamazepine was withdrawn about three years later.

From the age of ten symptoms of myasthenia gravis appeared: dysarthria with nasal pronunciation, dysphagia, variable ptosis, and reduced endurance. The symptoms were most obvious in the afternoon and evening. The edrophonium test was positive, EMG was consistent with myasthenia gravis, and acetylcholine receptor antibodies were positive (90 nmol/L, reference range 0.0 - 0.4 nmol/L). MRI disclosed a small lacuna in the lower thoracal medulla.

She was put on pyridostigmine and experienced some improvement. However, she had still significant symptoms and went on to thymectomy at the age of eleven years. After this she improved remarkably, and she has not experienced any further deterioration so far. The thymus showed lymphofollicular hyperplasia. Her haplotype has so far not been determined.

Having read the above-mentioned letter [[1]], it is reasonable to suspect that even in this girl myasthenia gravis may have been induced by carbamazepine. During the last 10 years we have seen only two additional children with myasthenia gravis in our department. Both were girls. None of them had previously been treated with carbamazepine. One was antibody negative, the other had a low level of 4.9 nmol/L.

References

• 1 Kurian M A, King M D. Antibody positive myasthenia gravis following treatment with carbamazepine - a chance association?.  Neuropediatrics. 2003;  34 276-277