MT-CO1 and palmoplantar keratosis: A previously reported homplasmic pathogenic sequence change in the mitochondrial mitCOX1 (also known as MT-CO1 gene; NC_012920: m.7445A>G (Martin et al., 2000) was identified in a 1-year-old infant with sensorineural hearing loss, palmoplantar keratosis and other extra palmoplantar cutaneous features further described in an already published case report (Moreno-Artero et al., 2022) (#P47 in Table 2).