The co-existence of myasthenia gravis in patients with myositis: A case series

Abstract

Objective Myositis and myasthenia gravis (MG) are both autoimmune disorders presenting with muscle weakness. Rarely, they occur simultaneously in the same patient. Since the management of myasthenia gravis differs from that of myositis, it is important to recognize when patients have both diseases. We reviewed the cases of 6 patients with both myositis and MG to identify clinical features that suggest the possibility of co-existing MG in myositis patients. Methods We identified 6 patients with dermatomyositis or polymyositis and MG. We reviewed their medical records to assess their clinical presentations, laboratory findings, and electrophysiological features. Results All 6 patients had definite dermatomyositis or polymyositis by the criteria of Bohan and Peter as well as electrophysiologic and/or serologic confirmation of MG. Among overlap patients, 5/6 (83%) had bulbar weakness, 2/6 (33%) had ptosis, and 1/6 (17%) had diplopia. Fatigable weakness was noted by 5/6 (83%) patients. Treatment with pyridostigmine improved symptoms in 5/6 (83%). High dose steroids were associated with worsening weakness in 2/6 (33%) patients. Conclusions Prominent bulbar symptoms, ptosis, diplopia, and fatigable weakness should suggest the possibility of MG in patients with myositis. A suspicion of MG may be confirmed through appropriate electrophysiologic and laboratory testing. In those with myositis-MG overlap, high dose steroids may exacerbate symptoms and pryidostigmine may play an important therapeutic role.

Abnormal spontaneous activity on needle electromyography in myasthenia gravis

“…A concomitant myositis cannot be entirely excluded in patients 2 and 3 without a muscle biopsy, but the normal CK speaks strongly against it. Reports of MG and concomitant myositis are rare, and most have been associated with elevated CK . None of our patients had ptosis or ophthalmoparesis, further confounding the clinical picture between myopathy and junctionopathy.…”

Simultaneous Combined Myositis, Inflammatory Polyneuropathy, and Overlap Myasthenic Syndrome

“…In a recent study, six patients with concurrent MG and inflammatory myopathy (dermatomyositis or polymyositis) were reported, with also twenty other cases found in the medical literature since 1976: most of these patients had no thymic hyperplasia, and the main myasthenic manifestations were bulbar weakness (83%), limb weakness (83%), ptosis (33%), and diplopia (17%) [5]. The presence of pathological lesions in MG is not recent and was observed early in the beginning of the twentieth century.…”

Dermatomiositis y miastenia gravis: una asociación infrecuente con implicaciones terapéuticas

“…La asociación de MG a MII es muy infrecuente, habiéndose comunicado hasta la actualidad 26 casos [3][4][5][6][7][8][9] . Es importante conocer esta asociación ya que tiene implicaciones terapéuticas.…”

“…Otra enfermedad autoinmune que cursa con debilidad muscular, la miastenia gravis (MG), también puede asociarse a las MII [3][4][5][6][7][8][9] . La MG es infrecuente, con una prevalencia estimada de 140 casos/10 6 habitantes 10 .…”