Inclusion body myositis belongs to the group of idiopathic inflammatory myopathies. Two processes, one autoimmune and the other degenerative, appear to occur in parallel. There are two forms of inclusion body myositis, hereditary and sporadic. Case report: 47-year-old woman with muscle weakness and atrophy of the distal and proximal muscles, and involvement of quadriceps and deep finger flexors was admitted for neuromuscular evaluation. These changes have been started gradually and insidiously over three years. Electromyography findings were nonspecific and for this reason in the beginning of the disease it was misdiagnosed as demyelization peripheral neuropathy. Muscle biopsy, with the presence of characteristic structures such as rimmed vacuoles and amyloid deposits definitely confirmed the diagnosis of inclusion body myositis. Conclusion: There are several difficulties in the diagnosis of inclusion body myositis as nonspecific EMG findings and overreliance on electrophysiology and lack of the cardinal histological features in muscle biopsy. Although this disease is rare and incurable, making the correct diagnosis is crucial to directing the patient to physical therapy for weakness and occupational therapy to improve a patient’s ability in activities of daily living.