Here we report the first pediatric case of restrictive cardiomyopathy secondary to a de novo mutation in the cardiac myosin heavy chain gene MYH7. The clinical course is characterized by an early onset of disease, mild hypertrophy of the left ventricle and a very short evolution to death. Because of the location of the mutation in the hinge region between the rod part and the globular head of the myosin molecule, it is possible that restrictive cardiomyopathy resulted from an impairment of flexion/extension of myosin heads during the contraction/relaxation cycle.