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|LETTER TO EDITOR
|Year : 2020 | Volume
| Issue : 2 | Page : 495-496
Skeletal Myopathy in a Male Patient with Anorexia Nervosa
Constantinos Papadopoulos, Vasiliki Zouvelou, George K Papadimas
1st Department of Neurology, University of Athens, Medical School, Eginition Hospital, 72, Vas. Sophias Avenue, Athens, Greece
|Date of Web Publication||15-May-2020|
1st Department of Neurology, University of Athens, Medical School, Eginition Hospital, 72, Vas. Sophias Avenue, Athens - 11528
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Papadopoulos C, Zouvelou V, Papadimas GK. Skeletal Myopathy in a Male Patient with Anorexia Nervosa. Neurol India 2020;68:495-6
Skeletal muscle can be affected secondarily by various systemic diseases such as infectious, rheumatic, metabolic, and endocrinological disorders. Muscle involvement in anorexia nervosa, with preferential affection of type 2 muscle fibers has been first reported by Essén et al. Subsequent reports confirmed muscular involvement in anorexia nervosa patients in the form of progressive myopathy, or as episodes of rhabdomyolysis. Causes could include metabolic abnormalities, vitamin deficiency, electrolyte imbalance, protein-energy malnutrition, or combinations of these, defective anaerobic glycolysis, hypercortisolemia,, and drug abuse with or without electrolyte imbalance. Most reported cases of anorexia nervosa along with muscular involvement addresses patients with the already diagnosed disease and other comorbidities such as hematological or metabolic complications or drug abuse.,,, Herein, we report a case of a young man referred to our neuromuscular outpatient clinic for the evaluation of an underlying myopathy. This case is interesting because no suspicion of an eating disorder was previously raised before, and the diagnosis of anorexia was primarily based on the clinical history and the progressive course of his muscular weakness.
A 32-year-old male presented with a one-year history of slowly progressive proximal symmetric upper and lower limb weakness and lack of endurance. Upon presentation, the patient weighed 50 kg (actual BMI = 17) and reported a weight-loss of 60 kg over the last two years. Clinical evaluation revealed mild neck flexor weakness (grade 4/5 on MRC scale), difficulty in rising from squatting and lying position, and myoedema upon percussion of biceps brachii muscle. The electromyographic evaluation showed short amplitude polyphasic motor units and rare high-frequency discharges (myotonic discharges), while nerve conduction studies were normal. His creatine kinase levels were elevated (970 U/L; normal range <195 U/L). All other laboratory tests, including an exercise forearm test, were normal. Due to the presence of myotonic discharges on electromyography genetic testing for myotonic dystrophy type 1 and 2 were performed prior and averred negative. To exclude other myopathies presenting with myotonic discharges on electromyography such as myofibrillar, metabolic, and inflammatory myopathies; a left vastus lateralis muscle biopsy was performed. Muscle biopsy showed muscle fiber atrophy (mean diameter 25,87 μm, SD: ± 13,98), some atrophic fibers presenting angular morphology, while there were numerous nuclear clumps [Figure 1]a. ATPase staining at pH 9.4 revealed a mean diameter of type 1 muscle fibers of 38,75 μm (SD: ± 12,06) and a preferential atrophy of type 2 muscle fibers with a mean diameter of 16,70 μm (SD: ± 5,37). There was no fiber type predominance [Figure 1]b. Psychiatric evaluation during hospitalization revealed an intense fear of weight gain with a disturbing experience of body weight shape and a restricted eating with reduced energy intake compatible with the diagnosis of anorexia nervosa according to the of diagnostic criteria in the diagnostic and statistical manual of mental disorders V (DSM-V).
|Figure 1: (a) H and E staining showing muscle fiber atrophy, atrophic fibers presenting angular and nuclear clumps (×20). (b) ATPase staining at pH 9.4 showing preferential atrophy of type 2 (dark stained) muscle fibers (×20)|
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Muscular weakness has been reported among patients with anorexia nervosa and is attributed to a probable underlying metabolic myopathy., Upon clinical examination, myoedema, a muscle mounting upon percussion has been reported as a useful clinical sign and the most prominent histopathological finding is muscle fiber type atrophy, involving preferentially type 2 fibers. This selective atrophy of glycolytic type 2 fibers may be partly due to an underlying defect of anaerobic glycolysis as it has been suggested by a blunted blood lactate response to exercise in some cases. Our patient presented with a proximal myopathy in the context of anorexia nervosa. Clinical evaluation revealed the presence of myoedema upon percussion of biceps brachii muscle and electrophysiological studies showed myopathic traces and, surprisingly, high-frequency discharges that have been not previously described in anorexia nervosa related myopathy.
Myoedema is an electrically silent mounding of muscle, following percussion, probably due to increased irritability of muscle membrane. It has been reported in healthy individuals, in hypothyroid myopathy, and traditionally in malnourished and vitamin deficient individuals., In anorexia nervosa patients, the presence of myoedema probably reflects the combined effects of vitamin deficiency, malnutrition, and generalized cachectic state on skeletal muscle.
High-frequency discharges have been not previously described in anorexia nervosa related myopathy. They are nonspecific and have been reported in various non-myotonic myopathies such as myofibrillar, metabolic inflammatory, and toxic myopathies and in denervation processes. Muscle biopsy did not show any findings compatible with these diagnoses and only revealed some denervation-like features with angulated atrophic fibers and nuclear clumps. These findings have been already reported in anorexia nervosa muscles but the lack of fiber type grouping, predominant type 2 fiber atrophy and normal nerve conduction studies have pointed away from true neurogenic atrophy. Selective type 2 muscle fiber atrophy has been associated with a variety of conditions such as excessive weight loss, disuse, ageing, systemic diseases such as paraneoplastic and corticosteroid myopathy. Hypercortisolemia is a known endocrine disturbance of anorexia nervosa and excessive endogenous glycocorticosteroids probably contribute to this selective type 2 atrophy and the pathogenesis of myopathy. Nevertheless, cortisol levels were normal in our patient. Therefore, in our case, where there was no evidence of other systemic complications of anorexia nervosa, myopathy is a direct effect of protein and energy malnutrition on skeletal muscle as it has been previously suggested.
In conclusion, muscle weakness and lack of endurance in anorexia nervosa patients are not only secondary to endocrine and metabolic disturbances but may also be related to a true underlying anorexia nervosa-related myopathy with distinct clinical, electrophysiological, and histological findings. Clinicians should be aware of myopathy related to anorexia nervosa, that rarely, as in our case, can precede other manifestation of the disease. It is characterized by symmetrical, proximal and axial weakness, presence of myoedema upon clinical examination, myopathic traces, and sometimes high-frequency discharges, in needle electromyography and selective type 2 fiber atrophy in muscle biopsy.
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The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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