We reported here clinical, genetic evaluations and molecular analysis of
mitochondrial DNA (
mtDNA) in two Han Chinese families carrying the known mitochondrial
12S rRNA A1555G mutation. In contrast with the previous data that
hearing loss as a sole phenotype was present in the maternal lineage of other families carrying the A1555G mutation, matrilineal relatives among these two Chinese families exhibited both
hearing loss and
hypertension. Of 21 matrilineal relatives, 9 subjects exhibited both
hearing loss and
hypertension, 2 individuals suffered from only
hypertension and 1 member had only
hearing loss. The average age at onset of
hypertension in the affected matrilineal relatives of these families was 60 and 46 years, respectively, whereas those of
hearing loss in these two families were 33 and 55 years, respectively. Molecular analysis of their
mtDNA identified distinct sets of variants belonging to the Eastern Asian haplogroup D5a. In contrast, the A1555G mutation occurred among other
mtDNA haplogroups D, B, R, F, G, Y, M and N, respectively. Our data further support that the A1555G mutation is necessary but by itself insufficient to produce the clinical phenotype. The other modifiers are responsible for the phenotypic variability of matrilineal relatives within and among these families carrying the A1555G mutation. Our investigation provides the first evidence that the
12S rRNA A1555G mutation leads to both of
hearing loss and
hypertension. Thus, our findings may provide the new insights into the understanding of pathophysiology and valuable information for management and treatment of maternally inherited
hearing loss and
hypertension.