Globe Subluxation following Long-Term High-Dose Steroid Treatment for Myasthenia Gravis

Abstract

This case report describes the unusual presentation of a globe subluxation following long-term high-dose oral steroid treatment for myasthenia gravis (MG). The patient presented initially with fluctuating vertical diplopia. Auto-antibodies against the acetylcholine receptor were weakly positive, confirming the diagnosis of MG. After initial treatment with pyridostigmine, the disease evolved to generalized MG. Plasmapheresis and high-dose steroids were started subsequently. As a side effect of this treatment the patient gained about 30 kg in weight and developed steroid myopathy and a prominent cushingoid facies with bilateral exophthalmos. A year after his initial diagnosis he experienced a spontaneous globe subluxation on the left eye. He was able to immediately reposition the globe manually himself. Four months later a new subluxation occurred. Because of these aforementioned severe side effects of the steroid treatment, the methylprednisolone was tapered and replaced by tacrolimus. After about 6 weeks the patient went into remission. We believe, that the spontaneous globe subluxations were caused by a weakness of the extraocular muscles in combination with a significant gain of intraorbital fat tissue, both induced by cumulative, excessive steroids. Steroids are often necessary in the treatment of MG; however, most of the time a high dose of 64 mg is not needed for ocular MG and especially the continuation of a dose of 58 mg or more for a long period is not recommended. Careful follow-up is obligatory to timely recognize side effects. In case of severe side effects or the need for long-term treatment, the use of other immunosuppressive therapies should be considered. Extra care and caution is recommended in patients who are anatomically predisposed with proptosis.