Belkheir, Aziza Miriam; Reunert, Janine; Elpers, Christiane; Heuvel, Lambert van den; Rodenburg, Richard; Seelhöfer, Anja; Rust, Stephan; Jeibmann, Astrid; Frosch, Michael; Marquardt, Thorsten: Severe Form of ßIV-Spectrin Deficiency With Mitochondrial Dysfunction and Cardiomyopathy—A Case Report