A maternally inherited diabetes and deafness patient with the 12S rRNA m.1555A>G and the ND1 m.3308T>C mutations associated with multiple mitochondrial deletions

► We report a patient with maternally inherited type 2 diabetes and deafness (MIDD). ► We detected the mitochondrial m.3308T>C and m.1555A>G mutations in muscle and blood. ► We revealed the presence of multiple mitochondrial deletions in the skeletal muscle. ► The deletions remove several tRNA and protein-coding genes. Maternally inherited diabetes and deafness (MIDD) is a mitochondrial syndrome characterized by the onset of sensorineural hearing loss and diabetes in adults. Some patients may have other additional clinical features common in mitochondrial disorders such as pigmentary retinopathy, ptosis, cardiomyopathy, myopathy and renal affections. We report a 40-year-old Tunisian patient presenting maternally inherited type 2 diabetes and deafness (MIDD). A molecular genetic analysis was conducted in the patient and his twin sister, but no reported mutations in the tRNALeu(UUR) and tRNAGlu genes were found, especially the two mitochondrial m.3243A>G and the m.14709T>C mutations in muscle and blood leukocytes. The results showed the presence of the mitochondrial NADH deshydrogenase 1 (ND1) homoplasmic m.3308T>C mutation the 2 tested tissues (blood leukocytes and skeletal muscle) of the proband and in the patient’s sister blood leukocytes. In addition, we identified the mitochondrial 12S rRNA m.1555A>G mutation in muscle and blood leukocytes. The Long-range PCR amplification revealed the presence of multiple deletions of the mitochondrial DNA extracted from the patient’s skeletal muscle removing several tRNA and protein-coding genes. Our study reported a Tunisian patient with clinical features of MIDD in whom we detected the 12S rRNA m.1555A>G and the ND1 m.3308T>C mutations with mitochondrial multiple deletions.