SDHD and viral infectious disease: Previously, compound heterozygous variants in SDHD [6], including the same p.(Glu69Lys) variant identified here and a c.479G > T; p.(Ter160LeuextTer3) alteration (c.[205G > A];[479G > T];p.[(Glu69Lys)];[(Ter160LeuextTer3)]), were identified as the likely candidate cause of disease in a Swiss child presenting with developmental regression following a viral infection, at 3 months.