317 Myasthenia Gravis and Asthma, Relationship between Two Different Disorders of the Immune System

BACKGROUND: Myasthenia gravis is an autoimmune disease caused by absence of neuromuscular transmission due to antibodies directed against the nicotinic AChR located at the neuromuscular junction. The main symptoms include muscle weakness in the affected muscles, which is worse after its use. Diagnosis is made upon clinical manifestations and finding of IgG. Only 80 to 90% of patients with generalized disease are positive to these antibodies, and 30 to 50% with ophthalmologic manifestations. Other immunological alteration found in these patients is an overexpression of the low affinity IgE receptor (CD23). Asthma is characterized by shortness of breath, cough, wheezing and chest tightness caused by inflammation and a reversible contraction of bronchial smooth muscle. Immunologically is associated with a Th2 cytokine profile, mainly Il-4, Il-5, Il-13 and an increased IgE. METHODS: Allergic and autoimmune diseases represent an altered response of the immune system. Here we discuss the case of a patient who presented with an allergic disease at first then years later developed an autoimmune disease. RESULTS: Our patient had been diagnosed with persistent allergic rhinitis and asthma since 1992. He had been treated with inhaled corticosteroids, bronchodilators, intranasal corticosteroids, antihistamines and specific immunotherapy with control of symptoms. In June 2010 he noticed diplopia, palpebral ptosis and muscle weakness in upper extremities diagnosed with Myastenia gravis and started treatment with piridostigmine with adequate control of muscular symptoms. No thymoma was identified. CONCLUSIONS: It has been noted the possible relationship between allergic and autoimmune diseases since in both there is an alteration in the regulatory mechanisms of the immune system. In this patient, we found the association between asthma and 19 years later the development of myasthenia gravis. Some of the explanations for this kind of association is the expression of CD23 in myasthenia gravis, which is a receptor found in B cells, among others, responsible of the increased production of IgE. Besides, autoimmune and allergic diseases share some pathogenic characteristics such as their influence by viral infections. They are one of the main factors associated with asthma exacerbations and it is suggested that they cause tissue damage, exposure to self-antigens and molecular mimicry.