SPEG and hydrops fetalis: Figure 1 shows the location and mutation type of all reported SPEG variants. Two patients lacking centralized myonuclei were diagnosed with non-specific CM [44,50]. Additional clinical features frequently observed in SPEG-related patients include respiratory issues, ophthalmoplegia, and scoliosis [8,43,44,50,51]. Further, reduced protein levels of SPEG have also been found as potential contributors to the development of heart failure (HF) and atrial fibrillation [14,21].