Spinal muscular atrophy belongs to a group of muscle diseases characterized by the destruction of the motor neurons of the spinal cord. It is an inherited autosomal recessive disease, and in approximately 2% of cases it occurs de novo. The disease is caused by sequence variants of the SMN1 gene within the 5q13 region of chromosome 5. The SMN1 gene is responsible for the production of the SMN protein, which has a role in maintaining alpha-motoneurons in the anterior horn of the spinal cord. Due to the lack of SMN protein, there is a loss of motor neurons which leads to denervation of muscle fibers and the appearance of muscle weakness and atrophy. The functional deficiency of the SMN1 gene is partially compensated by the SMN2 gene, and the number of its copies correlates with the severity of the clinical presentation of the disease. SMA shows phenotypic variation, and it is classified clinically into four SMA types, with type 0 as the most severe form of the disease. The classification of SMA subtypes is determined by the number of copies of the SMN2 gene, by the age of onset, as well as clinical severity. Early identification of affected infants prior to the presentation of clinical symptoms has been accomplished by newborn screening. Methods of molecular genetic testing are standard in diagnostic testing. Treatment can be supportive, and the greatest emphasis is on disease-modifying agents: nusinersen, risdiplam and onasemnogen abeparvovec. Early diagnosis and disease-modifying agents have led to a major breakthrough in the treatment of SMA patients.