Mitochondrial diseases caused by mutations of the POLG gene: problems of differential diagnosis

The article presents a review of current literature data relating to mitochondrial diseases associated with POLG-gene mutations. Diseases of this group have diverse and non-specific clinical manifestations, which makes their diagnosis a difficult task. Such diseases can develop as a result of mutations in their own mitochondrial DNA or nuclear cell genes, similar clinical manifestations, however, may differ in severity of flow and prognosis. The onset of these diseases can occur in the age range from early childhood to adulthood. Based on analysis of various literature sources, modern views on etiology, pathogenesis, clinical and diagnostical characteristics and therapeutic approaches to POLF-related mitochondrial diseases were generalized and systematically examined. Clinical case of a child with mitochondrial neurogastrointestinal encephalopathy, which is an atypical manifestation of POLG-gene mutations was also presented. In the clinical case presented, despite an increase in transaminases in the patient in history, no further liver damage characteristic of Alpers syndrome was observed. Also, the child did not develop catastrophic epileptic seizures resistant to therapy, however, a relatively mild course of epileptic encephalopathy was registered. However, the clinic was dominated by recurrent vomiting, weight loss, refusal to eat and signs of gastrointestinal dysfunction according to instrumental examinations. In this case, molecular genetic research was crucial for the diagnosis. In our opinion, pediatric physicians should have a certain level of alertness and promptly refer children with suspected mitochondrial disease to children's neurologists. Despite the tragic prognosis of certain diseases of this group, errors in their diagnosis are unacceptable. Accurate diagnosis should be made as early as possible. Today, this is possible only with the help of neuroradiological and molecular genetic methods.