IRC21 has homology to NADPH cytochrome B5 oxidoreductase, which is linked to insulin-dependent diabetes in mice, while IRC15 resembles mammalian mitochondrial dihydrolipoamide dehydrogenase, associated with a number of human diseases including Alzheimer disease [62,63]. The gene discussed is CYB5R4; the disease is early-onset autosomal dominant Alzheimer disease.