“…Familial MD is observed in 8%-9% of sporadic cases in populations of European descent [22,23]. It has been described in Caucasians from United Kingdom [24], Brazil [25], Sweden [26], Finland [23,27], Germany [28] and Spain [23]. Although most families described have an autosomal dominant pattern of inheritance, familial MD shows genetic heterogeneity, and mitochondrial and recessive inheritance patterns are also observed in some families [22].…”