Myasthenia gravis is an autoimmune disease affecting the skeletal neuromuscular junction. The clinical presentation of myasthenia gravis is subsequent to release of autoantibodies against postsynaptic nicotinic acetylcholine receptor in skeletal muscles or in some cases autoantibodies against muscle specific receptor tyrosine kinase are released. This leads to muscle weakness with repetitive work. The symptoms are fluctuant and presents with relapses and remissions. It is known to resolve spontaneously in some patients, but in most of the patients it persists for life. The disease has dynamic course and can occur at any age, but usually females are affected at a younger age (around 30 years); whereas, males are affected at a later part of life (after 50 years of age).
What Psychiatric Disorder Is Most Commonly Associated With Myasthenia Gravis?
Apart from motor disabilities in myasthenia gravis, psychological disorders have also been implicated in the disease. Since the disease is chronic, debilitating and life threatening if respiratory distress occurs, psychological disorders are commonly associated with it. There have been very few studies that have researched the psychological symptoms of the disease. Some studies have shown increased incidence of epilepsy in these patients, some have shown increased prevalence of sleep disorders and cognitive impairment due to the role of cholinergic system in the disease. Most of the data on neurological aspect of the disease is old with poor methodology; therefore there is no clear consensus regarding the psychiatric pathology of the disease.
The most commonly associated psychiatric conditions to myasthenia gravis are anxiety disorders, such as generalized anxiety disorder or panic disorder, in addition to depressive disorders. Both anxiety and depression were more prevalent in myasthenia gravis patients than normal population. There is scarcity of data regarding the prevalence and the cause of these psychiatric disorders in myasthenia gravis. Researchers are biased regarding the etiology of the neurological symptoms. Some consider it squeal to the chronicity and debilitating nature of the disease progression; while others hypothesize that there might be CNS involvement in the pathogenesis of psychiatric involvement.
There should be an understanding of both psychiatric conditions and myasthenia gravis, since overlapping symptoms may either delay diagnosis of either conditions or may lead to unnecessary drug treatment. The overlapping symptoms of both the diseases include fatigue, reduced energy and dyspnea. Both these conditions should be recognized early in the course of the disease to facilitate appropriate treatment for both the conditions.
Since, there is an intimate relationship between both myasthenia gravis and psychiatric symptoms; there should be further studies to help in understanding their relation better that would improve the quality of life during the course of the diseases.
Risk Factors For Myasthenia Gravis
Myasthenia gravis can be triggered or worsened by many factors, such as surgery, stress, immunization, infection, warm weather, menstruation, pregnancy, and worsening of medical conditions, such as cardiac, renal or autoimmune diseases. Certain medications have played an important role in aggravating or precipitating the disease. These include penicillamine, anticholinergics, ketamine, diazepam, halothane, ciprofloxacin, aminoglycosides, ampicillin, clindamycin, phenytoin, lithium, propranolol, verapamil, timolol, curare, vecuronium, procainamide, magnesium, quinidine, chloroquine, phenothiazines, chlorpromazine and procainamide.
Clinical Presentation Of Myasthenia Gravis
The most common symptom associated with myasthenia gravis is weakness without any pain. However, pain subsequent to muscle strain may be noted. The hallmark of the disease is that the weakness is exacerbated with repeated use of muscles leading to increased fatigue. Therefore, the symptoms are worse in the evening and better in the morning hours.
The most commonly affected muscles are the eye muscles leading to droopy eyelids and double vision that progress from mild to severe over weeks to months. Bulbar symptoms include the oropharynx musculature leading to their weakness that affects chewing, swallowing, speech and breathing. Difficulty chewing increases the chances of aspiration of food and aspiration pneumonia. In some patients breathing problems may cause respiratory failure. Skeletal muscles that are affected are basically the proximal muscles that assist in sitting, getting up from a chair, walking, climbing stairs.
- Inés Ybarra, Mariana & Kummer, Arthur & Comini-Frota, Elizabeth & Teotônio de Oliveira, José & Gomez, Rodrigo & Lucio Teixeira, Antonio. Psychiatric disorders in myasthenia gravis. Arquivos de neuro-psiquiatria. (2011) 69:176-9. http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0004-282X2011000200006
- Kulaksizoglu, I.B. Mood and Anxiety Disorders in Patients with Myasthenia Gravis. CNS Drugs (2007) 21(6): 473-81. https://www.ncbi.nlm.nih.gov/pubmed/17521227