Morphological and Histochemical Changes in Muscle Biopsies of Myasthenia Gravis with Atypical Clinical Presentation
Journal Title: Biomedical Journal of Scientific & Technical Research (BJSTR) - Year 2017, Vol 1, Issue 1
Abstract
We studied the morphological and histochemical changes in muscle biopsies from 6 cases with myasthenia gravis (MG), The patients were misdiagnosed at the initial presentation however they were all proved later by either histochmical and serological tests or improvement on mestinone therapy. Here, we described the changes seen in muscle biopsies of MG with atypical clinical presentation: atrophy of type II fibers; predominance of type I fibers; increased NADH staining at the neuromuscular junction (NMJ). The most consistent finding is marked reduction in acetylcholinesterease (AChE) activity at the end plates in all cases. The results of this study suggest that histochemical and acetylcholinesterase stains, in combination with clinical assessment can help to identify unsuspected cases of MG and can help to target the appropriate clinical investigations. Myasthenia gravis is an autoimmune disorder of neuromuscular junction with the circulating antibodies against acetylcholine receptor (AchR) caused by auto antibodies against the nicotinic acetylcholine receptor on the postsynaptic membrane and characterized by variable weakness and fatigability of oculobulbar and limb muscles [1]. It has a bimodal peak of incidence with first peak in the third decade and the second peak in the sixth decade [2]. The diagnosis is usually made on clinical and electrophysiological grounds. In the majority of patients, initial presentation is due to the involvement of extra ocular muscles. With the progression of the disease, facial, bulbar, proximal limb muscles, neck extensors, and diaphragm get involved [3]. This disease has a prevalence of 2/10000 population [4]. Untreated MG has a 10 year mortality of 20-30% and 85% of the patients are seropositive for acetyl choline antibodies [5]. Currently very little is known about the histochemical changes of muscle fiber types in MG. This may be due to that most of the patients are diagnosed by clinical examination, serology, EMG and nerve conduction studies. However, in some cases, the clinical picture may not be typical and serology tests may either be negative or not available. In this article, we are describing the muscle morphological and histochemical changes of MG. Knowing these changes are essential for neuropathogist so as not to miss cases with atypical presentation. We would like also to emphasize the value of routine use of acetylcholinesterease (AChE) staining in muscle biopsy.
Authors and Affiliations
Hussam Abu Farsakh, Altaf Ijmail
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