BACKGROUND: Late onset Pompe disease is a rare genetic disease from the group of the accumulation diseases, the main manifestation of which is the progressive myopathic syndrome. The difficulties of diagnostics are mainly related to the low awareness of the specialized physicians (neurologists, orthopaedists, rheumatologists, pulmonologists, pediatricians etc.) on the specific features of this disease, as well as to the low level of nosological specificity of the myopathic syndrome in general. Special importance of early diagnostics is due to the existence of pathogenetic therapy. Late diagnostics and delayed initiation of therapy lead to lower survival rate and higher rate of incapacitation among the patients. CLINICAL CASE DESCRIPTION: The patient aged 62 years, which for many years was under the supervision by neurologists with the diagnosis of osteochondrosis, based on the objective data, actually had a myopathic syndrome that was diagnosed and confirmed using the electroneuromyography. The detected findings included a decrease in the activity of the alpha-glucosidase enzyme, while the genetic examination that followed, allowed for detecting the presence of a mutation in the GAA gene. The dynamic changes of the disease were tracked with a background of taking pathogenetic therapy for 4 years. CONCLUSION: This clinical case demonstrates the many years of the patient’s way to being diagnosed with a rare genetic disease and, respectively, to the later initiation of therapy. The efficiency of treating the accumulation diseases directly depends on the extent of the pathological changes in the target organs, accumulated to the moment of diagnostics, which means — the earlier, the more effective.