Functional analyses, including RNA sequencing, immunofluorescence microscopy, and PDC activity, were hence performed due to high clinical suspicion for DLDD, revealing a monoallelic transcription of the DLD gene, reduced protein expression of DLD, and reduced PDC activity in the patient's fibroblasts, thus confirming the diagnosis of DLDD (see Figure S1). Here, DLD is linked to pyruvate dehydrogenase E3 deficiency.