LETM1 and diabetes mellitus: Linking clinical features with in vitro data, we found that fibroblasts expressing LETM1 variants c.[878T>A; 2094del], p.[Ile293Asn; Asp699Metfs13∗], which were identified in the individuals F1:S1 and F1:S2 affected with epilepsy, neurosensory deficiencies, and diabetes, displayed mitochondria with disturbed morphology and membrane potential, reduced LETM1 levels, and a severe decrease in respiratory proteins of CI and CIV.