RESUMO
The authors present a case of 75-year-old male patient with typical clinical and electroneuromyographic signs of Amyotrophic Lateral Sclerosis (ALS), manifested in 4 years after a diagnosis of generalized Myasthenia Gravis (MG) had been made. The aim of the article is to assess the possibility of pathogenetic integrated comorbidity of MG and ALS, which may have resulted from a common aberrant immune process and to emphasize the importance of detailed clinical analysis and adequate diagnostic methods essential for correct diagnosis and treatment. Only several cases of coexistence of MG and ALS have been described in medical literature. Exploring the pathogenetic association between MG and ALS may lead to dysregulation of thea immune system. Deficiency of T-regulatory cells, increased activity of atrophy-related atrogenes, anomalies of neuronal nitric oxide synthase can be found in both diseases. Immunoglobulin isolated from ALS patients can affect neuromuscular junction and activate AChRs, which plays an important role in the innervation and re-innervation of muscle fibers. Immunoglobulin also changes the function of Ca2+ channels. Blood level of circulatory Heat Shock Protein 70 (HSP70) antibodies in MG patients is elevated. HSP70 maintains normal conformation of cell proteins. Conversely, HSP70 antibodies cause HSP70's dysfunction and therefore, abnormal protein synthesis, which can be the main reason of neurodegenerative diseases, such as ALS. Experimental evidence indicates, that muscle and neuromuscular junctions may be initial targets of ALS. According to the "dying-back" hypothesis, neuromuscular junction damage and failure in MG patients may precede lower and upper motor neuron loss, and thus increase risk of developing ALS. Pathogenetic mechanisms of MG and ALS are the subjects of further studies. Refining the etiology of these two diseases will answer the question whether it is a transformation or a coexistence of MG and ALS in our case. The presented case demonstrates, that in spite of meeting all diagnostic criteria it is, sometimes, impossible to make the correct diagnosis. Only a detailed clinical analysis and adequate diagnostic methods contribute to correct diagnosis and adequate therapy.
