Myopathy in glycogen storage disease type IV: case report of a family

Aim. To study the clinical presentation and differential diagnosis of a rare hereditary disease glycogen storage disease type IV with progressive skeletal myopathy in a case report of a family. Materials and methods. Two patients were followed up in the specialized neurology unit of the regional clinical hospital and in the outpatient setting. Results. Long-term follow-up and examination in two clinically similar cases of myopathy in siblings allowed us to diagnose a hereditary metabolic disease. The congenital muscular form of glycogen storage disease type IV was manifested by myopathy and peripheral tetraparesis with the development of bone deformities. Difficulty in the diagnosis was due to isolated myopathy progression with no signs of liver involvement. The diagnosis was established with account of clinical manifestations, the progressive course of the disease, electromyography findings, and the results of molecular genetic testing for pathogenic mutations associated with hereditary neuromuscular diseases. Conclusion. Glycogen storage disease type IV can clinically manifest itself by progressive myopathy without liver involvement and changes in blood biochemistry. The presented clinical cases in siblings are identical. Myopathy does not have clinical features that are significant for the differential diagnosis with other hereditary neuromuscular diseases. Genetic testing identified a mutation in the GBE1 gene and is considered as the main diagnostic criterion of the disease.