Abstract
Myasthenia gravis (MG) is an autoimmune disorder involving the neuromuscular junction that frequently affects the extra-ocular muscles (EOMs). It has been described as a very rare cause of bilateral EOM atrophy, but histological analysis of such cases is lacking. A 66-year-old man presented with two months of right eyelid drooping and vertical diplopia. Examination showed bilateral ophthalmoparesis and complete right ptosis. The remainder of his exam was normal, and an MRI showed small EOMs. Acetylcholine receptor antibodies were elevated, establishing the diagnosis of MG. Oral corticosteroids and pyridostigmine followed by azathioprine improved his ptosis, but not his ophthalmoparesis. One year later he had surgical correction of his diplopia, and the resected superior rectus muscle showed complete replacement of EOM by connective tissue. MG can rarely cause bilateral EOM atrophy, which is characterized histologically by fibrosis in the muscle itself. Atrophy in the EOMs of a myasthenic patient may indicate a poor response to medical management alone.
Highlights
Myasthenia gravis (MG) is an autoimmune disease of the neuromuscular junction most often caused by autoantibodies targeting the post-synaptic acetylcholine receptor (AChR)
We present a case of anti-AChR antibody positive myasthenia gravis with atrophic and fibrotic extra-ocular muscles (EOMs) who had a poor response to medical therapy
Bilateral EOM atrophy is a rare entity that has been described in mitochondrial myopathies, myotonic dystrophy, and congenital fibrosis syndromes [5]
Summary
Myasthenia gravis (MG) is an autoimmune disease of the neuromuscular junction most often caused by autoantibodies targeting the post-synaptic acetylcholine receptor (AChR). While the primary site of pathology in MG is the neuromuscular junction, muscle changes occur. Lymphocyte infiltrates and muscle fiber atrophy are. (2014) Atrophy and Fibrosis of ExtraOcular Muscles in Anti-Acetylcholine Receptor Antibody Myasthenia Gravis. While modern diagnostic techniques have made muscle biopsy obsolete in the diagnosis of MG, an understanding of the spectrum of muscle pathology in MG can still be pertinent to clinical practice. We present a case of anti-AChR antibody positive myasthenia gravis with atrophic and fibrotic extra-ocular muscles (EOMs) who had a poor response to medical therapy
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