Myasthenia gravis in monozygotic twins. Clinical follow-up nine years after thymectomy.

Genetically proved monozygotic female twins in whom myasthenia gravis developed in their 20s initially had their disease well controlled with anticholinesterase medication. Because of increasing resistance to medication, twin 1 had her thymus removed, after which the symptoms decreased. Predicated on the improvement in her sister and the need for increasing medication to allay symptoms, and after proof of monozygosity, twin 2 also underwent thymectomy, with subsequent symptomatic improvement.