We present a 6-year-old girl with premature aging associated with mild myopathy, displaying muscle weakness, joint contractures and hyporeflexia. Genetic analysis revealed rare heterozygous point mutation in lamin A/C gene, g.428C>T. Cardiological evaluation showed atrial fibrillation, but we did not find signs of coronary heart disease, which is life-threatening cardiovascular complication in progeria. Electron microscopy of the muscle revealed abnormalities in nuclear architecture, i.e. blebbing, thick lamina and peripheral distribution of heterochromatin. As some diagnostic criteria characteristic for classic progeria are not fulfilled, this case could be regarded as atypical progeria associated with myopathy and atrial fibrillation. To our knowledge, this is the second case of such association described in the literature.