Inclusion body myopathy 3 (IBM3) is an autosomal dominant myopathy associated with a heterozygous missense mutation in the myosin heavy chain (MyHC) IIa gene (MYH2), changing the highly conserved and negatively charged glutamate at position 706 to the positively charged lysine (E706K). This region is important for myosin functioning during muscle contraction, because it undergoes conformational changes during adenosine triphosphate (ATP) hydrolysis. Clinical characteristics include congenital joint contractures, a progressive course in adulthood, and external ophthalmoplegia.
