TRMT5 and Global developmental delay: Combined oxidative phosphorylation deficiency 26 (COXPD26; MIM #616539), which includes developmental delay, shortness of breath, exercise intolerance, spasticity hyporeflexia, and hypotonia leading to the patient being unable to sit, stand, or walk without support, and decreased mitochondrial complex activity, is an autosomal recessive disorder characterized by a highly variable phenotype [1–3].