Homology modelling of the two putative pathogenic SDHD missense variants thus far associated with isolated autosomal recessive mitochondrial complex II deficiency [c.[205G > A];p.(Glu69Lys) and c.[275A > G];p.(Asp92Gly)] predicts disruption of non-covalent bonds between transmembrane helices and changes to complex II positioning in the inner mitochondrial membrane as likely outcomes (Supplementary Fig. S1a). This evidence concerns the gene SDHD and hyperinsulinemic hypoglycemia, familial, 4.