In 2017, we reported a novel form of isolated COX deficiency caused by a K101N variant of the COX4I1 gene encoding COX4-1 in a patient presenting with Fanconi anemia-like features, short stature and mild dysmorphism, while all the known Fanconi anemia (FA) gene sequences were intact. The gene discussed is COX4I1; the disease is mitochondrial complex IV deficiency, nuclear-type.